The role of triplet states in the emission mechanism of polymer light-emitting diodes (2009)
Arif, M., Mukhopadhyay, S., Ramasesha, S., Guha, S.
The blue emission of polyfluorene (PF) based light-emitting diodes (LEDs) is known to degrade due to a low energy green emission, which hitherto has been attributed to oxidative defects. By studying...
Tuning the bond-order wave phase in the half-filled extended Hubbard model (2009)
Kumar, Manoranjan, Ramasesha, S, Soos, ZG
Theoretical and computational studies of the quantum phase diagram of the one-dimensional half-filled extended Hubbard model (EHM) indicate a narrow bond-order wave (BOW) phase with finite magnetic...
Mahata, Partha, Raghunathan, Rajamani, Banerjee, Debamalya, Sen, Diptiman, Ramasesha, S, Bhat, SV, ...
Two new three-dimensional metal-organic frameworks (MOFs) [Mn-2(mu(3)-OH)(H2O)(2)(BTC)]-2 H2O, I, and [NaMn(BTC)], II (BTC=1,2,4-benzenetricarboxylate = trimellitate) were synthesized and their...
Dhers, Sebastien, Sahoo, Shaon, Costes, Jean-Pierre, Duhayon, Carine, Ramasesha, S, Sutter, Jean-Pascal
Heterometallic {3d-4f-5d} aggregates with formula [{LMe2Ni(H2O)Ln(H2O)4.5}2{W(CN)8}2]·15H2O, (LMe2 stands for N,N-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato) Schiff-base ligand) with Ln =...
Kumar, Manoranjan, Sarkar, Sujit, Ramasesha, S.
We use Abelian Bosonization and density matrix renormalization group method to study the effect of density on quantum phases of long range 1-D Bose-Hubbard model. We predict the existence of...
Tuning the bond order wave (BOW) phase of half-filled extended Hubbard models (2008)
Kumar, Manoranjan, Ramasesha, S., Soos, Z. G.
Theoretical and computational studies of the quantum phase diagram of the one-dimensional half-filled extended Hubbard model (EHM) indicate a narrow bond order wave (BOW) phase with finite magnetic...
Dimerization transition of alkali-TCNQ salts: Charge degrees of freedom near the CDW boundary (2008)
Kumar, Manoranjan, Ramasesha, S, Pascal, RA, Soos, ZG
Stacks of TCNQ − radical ions in 1 : 1 alkali salts are shown to be near the chargedensity- wave (CDW) boundary, where charge degrees of freedom induce strong dimerization δ.Charge-transfer...
A Theoretical Approach for Computing Magnetic Anisotropy in Single Molecule Magnets (2008)
Raghunathan, Rajamani, Ramasesha, S., Sen, Diptiman
We present a theoretical approach to calculate the molecular magnetic anisotropy parameters, $D_M$ and $E_M$ for single molecule magnets in any eigenstate of the exchange Hamiltonian, treating the...
Fully Symmetrized VB Based Technique for Solving Exchange Hamiltonians of Molecular Magnets (2008)
Sahoo, Shaon, Rajamani, Raghunathan, Ramasesha, S., Sen, Diptiman
Generally, the first step in modeling molecular magnets involves obtaining the low-lying eigenstates of a Heisenberg exchange Hamiltonian which conserves total spin and belongs usually to a...
Quantum Phase Analysis of Extended Bose-Hubbard Model (2008)
Kumar, Manoranjan, Sarkar, Sujit, Ramasesha, S.
We have obtained the quantum phase diagram of one dimensional extended Bose-Hubbard model using the density-matrix renormalization group and Abelian bosonization methods for different...
Mukhopadhyay, S, Topham, BJ, Soos, ZG, Ramasesha, S
The photoluminescence (PL) and electroluminescence (EL) of thin films of 1,1-bis[(di-4-tolylamino)phenyl]- cyclohexane (TAPC) are remarkably different. Similar PL and EL are instead observed in films...
Raghunathan, Rajamani, Ramasesha, S, Mathoniere, Corine, Marvaud, Valerie
The heptanuclear complex $[Mo(IV)(CN)_2(CN–CuL)_6]^{8+} $switches from a paramagnetic dark state corresponding to six spin-1/2 Cu(II) ions to a predominantly high spin S = 3 state, on prolonged...
Raghunathan, Rajamani, Ramasesha, S., Mathoniere, Corine, Marvaud, Valerie
The heptanuclear complex [Mo(IV)(CN)2(CN-CuL)6]8+ exhibits photomagnetism. An earlier microscopic model showed that the transition dipole moments for excitation in different spin manifolds are...
Soos, ZG, Mukhopadhyay, S, Ramasesha, S
The unusually different photoluminescence (PL) and electroluminescence (EL) of an organic film is related to disordered dipoles and charge–dipole interactions that reduce the transport gap of...
Kumar, Manoranjan, Ramasesha, S, Sen, Diptiman, Soos, ZG
In conformal field theory, key properties of spin-$^{(1/2)}$ chains, such as the ground state energy per site and the excitation gap, scale with dimerization \delta as $\delta ^\alpha$ with known...
Kumar, Manoranjan, Ramasesha, S, Sen, Diptiman, Soos, ZG
In conformal field theory, key properties of spin-$^{(1/2)}$ chains, such as the ground state energy per site and the excitation gap, scale with dimerization \delta as $\delta ^\alpha$ with known...
Soos, ZG, Mukhopadhyay, S, Ramasesha, S
The unusually different photoluminescence (PL) and electroluminescence (EL) of an organic film is related to disordered dipoles and charge–dipole interactions that reduce the transport gap of...
Venkatakrishnan, Thengarai S, Rajamani, Raghunathan, Ramasesha, S, Sutter, Jean-Pascal
A hexanuclear cyano-bridged $\{Mn^{II}_4Nb^{IV}_2\}$ cluster (1) bearing 2,2'-bipyridine (bpy) as the blocking ligand at manganese is obtained from the reaction of cis-$[MnCl_2(bpy)_2]$ and...
Venkatakrishnan, Thengarai S, Rajamani, Raghunathan, Ramasesha, S, Sutter, Jean-Pascal
A hexanuclear cyano-bridged $\{Mn^{II}_4Nb^{IV}_2\}$ cluster (1) bearing 2,2'-bipyridine (bpy) as the blocking ligand at manganese is obtained from the reaction of cis-$[MnCl_2(bpy)_2]$ and...
Kumar, Manoranjan, Ramasesha, S., Sen, Diptiman, Soos, Z. G.
In conformal field theory, key properties of spin-1/2 chains, such as the ground state energy per site and the excitation gap scale with dimerization delta as delta^alpha with known exponents alpha...
Ramasesha, S, Raghunathan, R, Ducasse, L, Sutter, JP, Mathonieere, C
Recent experiments show that the superexchange interaction in molecular clusters containing transition metal ions $A = Ni^{II}$ and $B = W^V, Nb^{IV} or Mo^V$ in some cases is...
Yan, Y, Mazumdar, S, Ramasesha, S
We report density-matrix renormalization group calculations of spin gaps in the quarter-filled correlated two-leg rectangular ladder with bond-dimerization along the legs of the ladder. In the small...
Raghunathan, Rajamani, Sutter, Jean-Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S.
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is...
Raghunathan, Rajamani, Sutter, Jean-Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and $M(M=Mo^V,W^V,Nb^I^V)$. Recent experiments show that in some systems this superexchange is...
Raghunathan, Rajamani, Ramasesha, S., Mathonière, Corine, Marvaud, Valérie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV)(CN)_2(CN-CuL)_6]^{8+}$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
Raghunathan, Rajamani, Sutter, Jean Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and $M(M=Mo^V, W^V, Nb^I^V)$. Recent experiments show that in some systems this superexchange is...
Yan, Y., Mazumdar, S., Ramasesha, S.
We report density-matrix renormalization group calculations of spin gaps in the quarter-filled correlated two-leg rectangular ladder with bond-dimerization along the legs of the ladder. In the small...
Raghunathan, Rajamani, Sutter, Jean Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and $M(M=Mo^V, W^V, Nb^I^V)$. Recent experiments show that in some systems this superexchange is...
Ramasesha, S, Raghunathan, R, Ducasse, L, Sutter, JP, Mathonieere, C
Recent experiments show that the superexchange interaction in molecular clusters containing transition metal ions $A = Ni^{II}$ and $B = W^V, Nb^{IV} or Mo^V$ in some cases is...
Raghunathan, Rajamani, Sutter, Jean-Pascal, Ducasse, Laurent, Desplanches, Cedric, Ramasesha, S.
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is...
Das, Mousumi, Ramasesha, S, Mazumdar, S
We investigate the possibility that high-energy singlet and triplet excited states with large electron-hole separations are generated in electron-hole recombination process, over and above the lowest...
Charge transport in DNA strands using fragment orbital theory (2005)
Fritsch, A, Ducasse, L, Castet, F, Ramasesha, S
A semi-empirical Valence-Bond/Hartree-Fock (VB/HF) method is developed to calculate one- and two-electron interactions between molecular fragments in conducting supramolecular stacks. This fragment...
Raghunathan, Rajamani, Ramasesha, S., Mathonière, Corine, Marvaud, Valérie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV)(CN)_2(CN-CuL)_6]^{8+}$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
High-Pressure Study of Adamantane: Variable Shape Simulations up to 26 GPa (2005)
Murugan, Arul N, Rao, RS, Yashonath, S, Ramasesha, S, Godwal, BK
We report simulations of adamantane by carefully combining ab initio and empirical approaches to enable simulations with internal degrees of freedom on crystalline adamantane up to a pressure of 26...
Jha, Prakash Chandra, Pati, Anusooya Y, Ramasesha, S
We have studied the nonlinear optical (NLO) properties of some donor -acceptor molecules with stilbene and azobenzene molecules as backbone.We have used the nitro group as the acceptor and...
Jha, Prakash Chandra, Pati, Anusooya Y, Ramasesha, S
We have studied the nonlinear optical (NLO) properties of some donor -acceptor molecules with stilbene and azobenzene molecules as backbone.We have used the nitro group as the acceptor and...
High-Pressure Study of Adamantane: Variable Shape Simulations up to 26 GPa (2005)
Murugan, Arul N, Rao, RS, Yashonath, S, Ramasesha, S, Godwal, BK
We report simulations of adamantane by carefully combining ab initio and empirical approaches to enable simulations with internal degrees of freedom on crystalline adamantane up to a pressure of 26...
Raghunathan, Rajamani, Ramasesha, S, Mathoniere, Corine, Marvaud, Valerie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV )(CN)_2(CN-CuL)_6]^8^+$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
Das, Mousumi, Ramasesha, S, Mazumdar, S
We investigate the possibility that high-energy singlet and triplet excited states with large electron-hole separations are generated in electron-hole recombination process, over and above the lowest...
Charge transport in DNA strands using fragment orbital theory (2005)
Fritsch, A, Ducasse, L, Castet, F, Ramasesha, S
A semi-empirical Valence-Bond/Hartree-Fock (VB/HF) method is developed to calculate one- and two-electron interactions between molecular fragments in conducting supramolecular stacks. This fragment...
Raghunathan, Rajamani, Ramasesha, S., Mathonière, Corine, Marvaud, Valérie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV)(CN)_2(CN-CuL)_6]^{8+}$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
Raghunathan, Rajamani, Sutter, Jean-Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S.
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is...
Raghunathan, Rajamani, Sutter, Jean-Pascal, Ducasse, Laurent, Desplanches, Cédric, Ramasesha, S.
Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is...
Raghunathan, Rajamani, Ramasesha, S., Mathonière, Corine, Marvaud, Valérie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV)(CN)_2(CN-CuL)_6]^{8+}$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
Raghunathan, Rajamani, Ramasesha, S, Mathoniere, Corine, Marvaud, Valerie
A theoretical model for understanding photomagnetism in the heptanuclear complex $[Mo(IV )(CN)_2(CN-CuL)_6]^8^+$ perchlorate is developed. It is a many-body model involving the active orbitals on the...
Das, Mousumi, Mazumdar, S., Ramasesha, S.
We extend our theory of electron--hole recombination in organic light emitting diodes to investigate the possibility that high energy singlet and triplet excited states with large electron--hole...
Chandra, Ravi V, Ramasesha, S, Sen, Diptiman
We propose a model which could explain some of the unusual magnetic properties observed for the onedimensional helical spin system $Co(hfac)_2NITPhOMe.$ One of these properties is that the...
Jha, Prakash Chandra, Das, Mousumi, Ramasesha, S
The correlated Pariser-Parr-Pople model Hamiltonian for interacting ð-electrons is employed for calculating the two-photon absorption (TPA) cross section in trans-stilbene and its derivatives using...
High Pressure Phase of Biphenyl at Room Temperature: A Monte Carlo Study (2004)
Murugan, Arul N, Chandra, Prakash Jha, Yashonath, S, Ramasesha, S
A new pressure-induced solid phase of biphenyl is reported at room temperature. Isothermal-isobaric ensemble variable shape simulation cell Monte Carlo calculations are reported on biphenyl at 300 K...
Chandra, V. Ravi, Ramasesha, S., Sen, Diptiman
We study a model which could explain some of the unusual magnetic properties observed for the one-dimensional helical spin system Co(hfac)_2 NITPhOMe. One of the properties observed is that the...
Jha, Prakash Chandra, Das, Mousumi, Ramasesha, S
The correlated Pariser-Parr-Pople model Hamiltonian for interacting ð-electrons is employed for calculating the two-photon absorption (TPA) cross section in trans-stilbene and its derivatives using...
Chandra, Ravi V, Ramasesha, S, Sen, Diptiman
We propose a model which could explain some of the unusual magnetic properties observed for the onedimensional helical spin system $Co(hfac)_2NITPhOMe.$ One of these properties is that the...
High Pressure Phase of Biphenyl at Room Temperature: A Monte Carlo Study (2004)
Murugan, Arul N, Chandra, Prakash Jha, Yashonath, S, Ramasesha, S
A new pressure-induced solid phase of biphenyl is reported at room temperature. Isothermal-isobaric ensemble variable shape simulation cell Monte Carlo calculations are reported on biphenyl at 300 K...
Mazumdar, S., Das, Mousumi, Ramasesha, S.
The low-lying singlet and triplet spectrum in conjugated polymers clearly show that the mechanism proposed by Lin et al. to explain their electric field dependence of singlet to triplet yield ratios...
Ramasesha, S, Mazumdar, S, Tandon, Kunj, Das, Mousumi
Using a time-dependent model many-body formulation, we follow the electron–hole recombination between a pair of oppositely charged polyene chains and triplet–triplet (T–T) scattering in...
Properties of a mixed-valent iron compound with the kagome lattice (2003)
Rao, CNR, Paul, Geo, Choudhury, Amitava, Sampathkumaran, EV, Raychaudhuri, Arup K, Ramasesha, S, ...
An organically templated iron sulfate of the formula $[HN(CH_2)_6NH] [Fe^I^I^IFe_2^I^I F_6(SO_4)_2]\cdot[H_3O]$ possessing the kagome lattice has been prepared and characterized by single-crystal...
Electron correlation effects in electron-hole recombination in organic light-emitting diodes (2003)
Tandon, Kunj, Ramasesha, S, Mazumdar, S
We develop a general theory of electron-hole recombination in organic light-emitting diodes that leads to formation of emissive singlet excitons and nonemissive triplet excitons. We briefly review...
Properties of a mixed-valent iron compound with the kagome lattice (2003)
Rao, CNR, Paul, Geo, Choudhury, Amitava, Sampathkumaran, EV, Raychaudhuri, Arup K, Ramasesha, S, ...
An organically templated iron sulfate of the formula $[HN(CH_2)_6NH] [Fe^I^I^IFe_2^I^I F_6(SO_4)_2]\cdot[H_3O]$ possessing the kagome lattice has been prepared and characterized by single-crystal...
Electron correlation effects in electron-hole recombination in organic light-emitting diodes (2003)
Tandon, Kunj, Ramasesha, S, Mazumdar, S
We develop a general theory of electron-hole recombination in organic light-emitting diodes that leads to formation of emissive singlet excitons and nonemissive triplet excitons. We briefly review...
Ramasesha, S, Mazumdar, S, Tandon, Kunj, Das, Mousumi
Using a time-dependent model many-body formulation, we follow the electron–hole recombination between a pair of oppositely charged polyene chains and triplet–triplet (T–T) scattering in...
Characterization of the Energy Structure and Adiabatic Magnetization Process of V15 (2002)
Rudra, Indranil, Saito, K., Ramasesha, S., Miyashita, Seiji
The energy structure of the V$_{15}$ is studied using exact diagonalization methods, and the adiabatic changes of the magnetization in the system with the sweeping field are investigated. We confirm...
Rudra, Indranil, Ramasesha, S., Sen, Diptiman
We study the low-energy properties of Heisenberg antiferromagnetic spin-1/2 and spin-1 systems on various clusters made up of triangles. Some of the clusters have a geometry similar to representative...
Electron correlation effects in electron-hole recombination in organic light-emitting diodes (2002)
Tandon, K., Ramasesha, S., Mazumdar, S.
We develop a general theory of electron--hole recombination in organic light emitting diodes that leads to formation of emissive singlet excitons and nonemissive triplet excitons. We briefly review...
Nonlinear optical properties of linear chain phosphazenes, (PN)x (2002)
Jha, Prakash Chandra, Krishnan, Anu, Das, Puspendu K, Ramasesha, S
The correlated Pariser–Parr–Pople model Hamiltonian for interacting \pi-electrons is employed for calculating frequency dependent linear polarizability as well as first and second...
Rudra, I, Raghu, C, Ramasesha, S
We have used a many-body model Hamiltonian to study the nature of the magnetic ground state of heterobinuclear complexes involving rare-earth and copper ions. We have taken into account all diagonal...
Raghu, C, Pati, Anusooya Y, Ramasesha, S
We have carried out density-matrix renormalization group calculations on the ground state of long polyacene oligomers within a Pariser-Parr-Pople (PPP) Hamiltonian. The PPP model includes long-range...
Model Exact Low-Lying States and Spin Dynamics in Ferric Wheels; Fe$_6$ to Fe$_{12}$ (2002)
Rudra, Indranil, Ramasesha, S., Sen, Diptiman
Using an efficient numerical scheme that exploits spatial symmetries and spin-parity, we have obtained the exact low-lying eigenstates of exchange Hamiltonians for ferric wheels up to Fe$_{12}$. The...
Nonlinear optical properties of linear chain phosphazenes, (PN)x (2002)
Jha, Prakash Chandra, Krishnan, Anu, Das, Puspendu K, Ramasesha, S
The correlated Pariser–Parr–Pople model Hamiltonian for interacting \pi-electrons is employed for calculating frequency dependent linear polarizability as well as first and second...
Properties of the low-lying electronic states of phenanthrene: Exact PPP results (2002)
Chakrabarti, Aparna, Ramasesha, S
We report properties of the exact low-lying states of phenanthrene, its anion and dianion within the Pariser-Parr-Pople (PPP) model. The experimentally known singlet states of the neutral molecule...
Raghu, C, Pati, Anusooya Y, Ramasesha, S
We have carried out density-matrix renormalization group calculations on the ground state of long polyacene oligomers within a Pariser-Parr-Pople (PPP) Hamiltonian. The PPP model includes long-range...
Properties of the low-lying electronic states of phenanthrene: Exact PPP results (2002)
Chakrabarti, Aparna, Ramasesha, S
We report properties of the exact low-lying states of phenanthrene, its anion and dianion within the Pariser-Parr-Pople (PPP) model. The experimentally known singlet states of the neutral molecule...
Rudra, Indranil, Raghu, C., Ramasesha, S.
We have used a many-body model Hamiltonian to study the nature of the magnetic ground state of hetero-binuclear complexes involving rare-earth and copper ions. We have taken into account all diagonal...
An alternate model for magnetization plateaus in the molecular magnet $V_{15}$ (2001)
Rudra, Indranil, Ramasesha, S, Sen, Diptiman
Starting from an antiferromagnetic Heisenberg Hamiltonian for the 15 spin-1/2 ions in $V_{15}$, we construct an effective spin Hamiltonian involving eight low-lying states (spin-1/2 and spin-3/2)...
Raghu, C., Pati, Y. Anusooya, Ramasesha, S.
We have carried out Density Matrix Renormalization Group (DMRG) calculations on the ground state of long polyacene oligomers within a Pariser-Parr-Pople (PPP) Hamiltonian. The PPP model includes...
Rudra, Indranil, Ramasesha, S, Sen, Diptiman
Beginning with a Heisenberg: spin Hamiltonian for the manganese ions in the Mn12Ac molecule, we find a number of model exact low-energy states of the system whose spectrum corresponds to the ordering...
Exact and Approximate Theoretical Techniques for Quantum Magnetism in Low Dimensions (2001)
Pati, Swapan K., Ramasesha, S., Sen, Diptiman
Quantum magnetism in low dimensions has been one of the central areas of theoretical research for many decades now. One of the key reasons for the long standing interest in this field has been the...
Dynamic Oscillations of Magnetization in High Spin Magnetic Clusters (2001)
Rudra, Indranil, Ramasesha, S.
We have studied the time evolution of magnetization of a high spin magnetic cluster in the ground state, in the presence of a sinusoidal axial magnetic field and a static transverse field by...
Formation cross-sections of singlet and triplet excitons in pi-conjugated polymers (2001)
Wohlgenannt, M, Tandon, Kunj, Mazumdar, S, Ramasesha, S, Vardeny, ZV
Electroluminescence in organic light-emitting diodes arises from a charge-transfer reaction between the injected positive and negative charges by which they combine to form singlet excitons that...
Raghu, C., Rudra, Indranil, Sen, Diptiman, Ramasesha, S.
Using an efficient numerical scheme that exploits spatial symmetries and spin parity, we have obtained the exact low-lying eigenstates of exchange Hamiltonians for the high nuclearity spin clusters,...
An alternate model for magnetization plateaus in the molecular magnet $V_{15}$ (2001)
Rudra, Indranil, Ramasesha, S, Sen, Diptiman
Starting from an antiferromagnetic Heisenberg Hamiltonian for the 15 spin-1/2 ions in $V_{15}$, we construct an effective spin Hamiltonian involving eight low-lying states (spin-1/2 and spin-3/2)...
An alternate model for magnetization plateaus in the molecular magnet V_15 (2000)
Rudra, Indranil, Ramasesha, S., Sen, Diptiman
Starting from an antiferromagnetic Heisenberg Hamiltonian for the fifteen spin-1/2 ions in V_15, we construct an effective spin Hamiltonian involving eight low-lying states (spin-1/2 and spin-3/2)...
Evaluation of low-energy effective Hamiltonian techniques for coupled spin triangles (2000)
Raghu, C, Rudra, Indranil, Ramasesha, S, Sen, Diptiman
Motivated by recent work on Heisenberg antiferromagnetic spin systems on various lattices made up of triangles, we examine the low-energy properties of a chain of antiferromagnetically coupled...
Magnetization of Mn_12 Ac in a slowly varying magnetic field: an ab initio study (2000)
Rudra, Indranil, Ramasesha, S., Sen, Diptiman
Beginning with a Heisenberg spin Hamiltonian for the manganese ions in the Mn_12 Ac molecule, we find a number of low-energy states of the system. We use these states to solve the time-dependent...
Evaluation of low-energy effective Hamiltonian techniques for coupled spin triangles (2000)
Raghu, C., Rudra, Indranil, Ramasesha, S., Sen, Diptiman
Motivated by recent work on Heisenberg antiferromagnetic spin systems on various lattices made up of triangles, we examine the low-energy properties of a chain of antiferromagnetically coupled...
Evaluation of low-energy effective Hamiltonian techniques for coupled spin triangles (2000)
Raghu, C, Rudra, Indranil, Ramasesha, S, Sen, Diptiman
Motivated by recent work on Heisenberg antiferromagnetic spin systems on various lattices made up of triangles, we examine the low-energy properties of a chain of antiferromagnetically coupled...
Pati, Swapan K, Ramasesha, S, Shuai, Z, Bredas, JL
We extend the symmetrized density-matrix renormalization-group method to compute the dynamic nonlinear optical coefficients for long chains. By computing correction vectors in the appropriate...
Anusooya, Y, Pati, Swapan K, Ramasesha, S
The phase diagram of halogen-bridged mixed-valence metal complexes (MX) has been studied using a two-band extended Peierls-Hubbard model employing the recently developed density-matrix...
Mazumdar, Sumit, Campbell, David, Clay, R Torsten, Ramasesha, S
Recently, Hiraki and Kanoda (HK) [1] observed charge ordering of a Wigner crystal type in a quarter-filled quasi- 1D organic charge transfer solid (CTS): sDI-DCNQId2Ag HK took 13C-NMR spectra from 3...
Exciton binding energy in the strong correlation limit of conjugated chains (1998)
Shuai, Z, Brédas, JL, Pati, SK, Ramasesha, S
By applying the numerically accurate symmetrized density-matrix renormalization-group method coupled with the extended Hubbard-Peierls model, we find that (i) the on-site Hubbard repulsion energy U...
Ring Currents in Condensed Ring Systems (1998)
Anusooya, Y, Chakrabarti, Aparna, Pati, Swapan K, Ramasesha, S
We have studied magnetism and aromaticity of polycyclic ring systems by analyzing ring currents for different circulations in these molecules. The technique employed for calculating ring currents...
Mazumdar, S., Ramasesha, S., Clay, R. T., Campbell, D. K.
Recent experiments indicate that the spin-density waves (SDWs) in (TMTTF)_2Br, (TMTSF)_2PF_6 and alpha-(BEDT-TTF)_2MHg(SCN)_4 are highly unconventional and coexist with charge-density waves (CDWs)....
Magnetization Properties of Some Quantum Spin Ladders (1998)
Tandon, Kunj, Lal, Siddhartha, Pati, Swapan K., Ramasesha, S., Sen, Diptiman
The experimental realization of various spin ladder systems has prompted their detailed theoretical investigations. Here we study the evolution of ground state magnetization with an external magnetic...
Structural instability in polyacene: A projector quantum Monte Carlo study (1998)
Srinivasan, Bhargavi, Ramasesha, S
We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls’ instability in a system marginally away from one dimension. We employ the projector...
Ring Currents in Condensed Ring Systems (1998)
Anusooya, Y, Chakrabarti, Aparna, Pati, Swapan K, Ramasesha, S
We have studied magnetism and aromaticity of polycyclic ring systems by analyzing ring currents for different circulations in these molecules. The technique employed for calculating ring currents...
Structural instability in polyacene: A projector quantum Monte Carlo study (1998)
Srinivasan, Bhargavi, Ramasesha, S
We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls’ instability in a system marginally away from one dimension. We employ the projector...
Pati, Swapan K, Ramasesha, S, Sen, Diptiman
We use the density matrix renormalization group (DMRG) method to study the ground and low-lying excited states of three kinds of uniform and dimerized alternating spin chain. The DMRG procedure is...
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We present in detail the recently developed multiconfigurational symmetrized projector quantum Monte Carlo method for excited states of the Hubbard model. We describe the implementation of the Monte...
Shuai, Z, Pati, Swapan K, Su, WP, Bredas, JL, Ramasesha, S
Using a symmetrized density-matrix renormalization-group formulation, we have investigated the electronic binding energy of the lowest optically allowed exciton (1B(u)) within an extended...
Anusooya, Y, Pati, Swapan K, Ramasesha, S
We report the symmetrized density matrix renormalization group (DMRG) study of neutral and doped oligomers of poly- para-phenylene (PPP) system within an extended Hubbard model. Model parameters are...
Pati, Swapan K., Ramasesha, S., Sen, Diptiman
We use the density matrix renormalization group (DMRG) method to study the ground and low-lying excited states of three kinds of uniform and dimerized alternating spin chains. The DMRG procedure is...
Shuai, S, Patil, S K, Bredas, J L, Ramasesha, S
Using a symmetrized density matrix renormalization group formulation, we have investigated the electronic binding energy (Eb) Of the lowest optically allowed exciton (1B) and the crossover behavior...
Shuai, Z., Bredas, J. L., Pati, S. K., Ramasesha, S.
The symmetrized density matrix renormalization group approach is applied within the extended Hubbard-Peierls model (with parameters U/t, V/t, and bond alternation \delta) to study the ordering of the...
Structural Instability in Polyacene : A Projector Quantum Monte Carlo Study (1997)
Srinivasan, Bhargavi, Ramasesha, S.
We have studied polyacene within the Hubbard model to explore the effect of electron correlations on the Peierls' instability in a system marginally away from one-dimension. We employ the projector...
Pati, Swapan, Chitra, R, Sen, Diptiman, Ramasesha, S, Krishnamurthy, HR
The ground-state ‘phase’ diagrams and some low-energy properties of isotropic antiferromagnetic spin- 1/2 and spin-1 chains with a next-nearest-neighbour exchange $J_2$ and an alternation...
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We present in detail the recently developed multiconfigurational symmetrized projector quantum Monte Carlo method for excited states of the Hubbard model. We describe the implementation of the Monte...
Anusooya, Y, Pati, Swapan K, Ramasesha, S
We report the symmetrized density matrix renormalization group (DMRG) study of neutral and doped oligomers of poly- para-phenylene (PPP) system within an extended Hubbard model. Model parameters are...
Pati, Swapan, Chitra, R, Sen, Diptiman, Ramasesha, S, Krishnamurthy, HR
The ground-state ‘phase’ diagrams and some low-energy properties of isotropic antiferromagnetic spin- 1/2 and spin-1 chains with a next-nearest-neighbour exchange $J_2$ and an alternation...
Ray, Paresh Chandra, Das, Puspendu Kumar, Ramasesha, S
Dynamic and static first hyperpolarizabilities $(\beta)$ of a series of benzoic and cinnamic acids in water have been investigated. These acids exist in a mixture of acidic and basic forms in...
Anusooya, Y., Pati, Swapan K., Ramasesha, S.
We report the symmetrized density matrix renormalization group (DMRG) study of neutral and doped oligomers of PPP system within an extended Hubbard model. Model parameters are determined by comparing...
Pati, Swapan K., Ramasesha, S., Sen, Diptiman
We report spin wave and DMRG studies of the ground and low-lying excited states of uniform and dimerized alternating spin chains. The DMRG procedure is also employed to obtain low-temperature...
Ramasesha, S., Pati, Swapan K., Krishnamurthy, H. R., Shuai, Z., Bredas, J. L.
A symmetrized Density Matrix Renormalization Group procedure together with the correction vector approach is shown to be highly accurate for obtaining dynamic linear and third order polarizabilities...
Srinivasan, Bhargavi, Ramasesha, S., Krishnamurthy, H. R.
We present in detail the recently developed multi-configurational symmetrized projector quantum Monte Carlo (MSPQMC) method for excited states of the Hubbard model. We describe the implementation of...
Symmetrized density-matrix renormalization-group method for excited states of Hubbard models (1996)
Ramasesha, S, Pati, Swapan K, Krishnamurthy, HR, Shuai, Z, Bredas, JL
We extend the density-matrix renormalization-group DMRG method to exploit parity, $C_2$ (rotation by \pi), and electron-hole symmetries of model Hamiltonians. We demonstrate the power of this method...
Anusooya, Y., Pati, Swapan K, Ramasesha, S.
The phase diagram of halogen-bridged mixed-valent metal complexes ($MX$) has been studied using a two-band extended Peierls-Hubbard model employing the recently developed Density Matrix...
Symmetrized projector quantum Monte Carlo studies of the ground state of $C_{60}$ (1996)
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We develop a symmetrized version of the projector quantum Monte Carlo SPQMC method which preserves the symmetries of the system by simultaneously sampling all symmetry-related Ising configurations at...
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We develop a multiconfigurational symmetrized-projector quantum Monte Carlo MSPQMC method to calculate excited-state properties of Hubbard models. We compare the MSPQMC results for finite Hubbard...
Variational Monte Carlo and Configuration Interaction Studies of $C_{60}$ and Its Fragments (1996)
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
The $C_{60}$ molecule and its fragments are studied using configuration interaction and variational Monte Carlo techniques, within the Hubbard model. Using benzene as a test case, we compare the...
Symmetrized PQMC Studies of the ground state of $C_{60}$ (1996)
Srinivasan, Bhargavi, Ramasesha, S., Krishnamurthy, H. R.
We develop a new $\it {symmetrized}$ version of the Projector Quantum Monte Carlo (SPQMC) method which preserves the symmetries of the system by simultaneously sampling all symmetry related Ising...
Pati, Swapan K., Ramasesha, S., Shuai, Z., Bredas, J. L.
We extend the symmetrized density matrix renormalization group (SDMRG) method to compute the dynamic nonlinear optic coefficients for long chains. By computing correction vectors in the appropriate...
Srinivasan, Bhargavi, Ramasesha, S., Krishnamurthy, H. R.
We develop a novel multi-configurational Symmetrized Projector Quantum Monte Carlo (MSPQMC) method to calculate excited state properties of Hubbard models. We compare the MSPQMC results for finite...
Variational Monte Carlo and Configurational Interaction Studies of $C_{60}$ and its Fragments (1996)
Srinivasan, Bhargavi, Ramasesha, S., Krishnamurthy, H. R.
The $C_{60}$ molecule and its fragments are studied using Configuration Interaction (CI) and Variational Monte Carlo (VMC) techniques, within the Hubbard model. Using benzene as a test case, we...
Pai, Ramesh V, Pandit, Rahul, Krishnamurthy, HR, Ramasesha, S
We use the density-matrix renormalization group to study the one-dimensional bosonic Hubbard model, with and without disorder. We obtain the gaps in all phases, certain correlation functions, and the...
Symmetrized DMRG Method for Excited States of Hubbard Models (1996)
Ramasesha, S., Pati, Swapan K., Krishnamurthy, H. R., Shuai, Z., Bredas, J. L.
We extend the density matrix renormalization group method to exploit Parity, $C_2$ (rotation by $\pi$) and electron-hole symmtries of model Hamiltonians. We demonstrate the power of this method by...
Pati, Swapan, Chitra, R., Sen, Diptiman, Ramasesha, S., Krishnamurthy, H. R.
We use the density matrix renormalization group method to study the ground state `phase' diagram and some low-energy properties of isotropic antiferromagnetic spin-$1 \over 2$ and spin-$1$ chains...
Phase diagram of the spin-one Heisenberg system with dimerization and frustration (1996)
Pati, S, Chitra, R, Sen, D, Krishnamurthy, HR, Ramasesha, S
We use the density matrix renormalization group method to study the groundstate "phase" diagram and some low-energy properties of an antiferromagnetic spin-1 chain with a next-nearest-neighbour...
Pai, Ramesh V, Pandit, Rahul, Krishnamurthy, HR, Ramasesha, S
We use the density-matrix renormalization group to study the one-dimensional bosonic Hubbard model, with and without disorder. We obtain the gaps in all phases, certain correlation functions, and the...
Phase diagram of the spin-one Heisenberg system with dimerization and frustration (1996)
Pati, S, Chitra, R, Sen, D, Krishnamurthy, HR, Ramasesha, S
We use the density matrix renormalization group method to study the groundstate "phase" diagram and some low-energy properties of an antiferromagnetic spin-1 chain with a next-nearest-neighbour...
Symmetrized density-matrix renormalization-group method for excited states of Hubbard models (1996)
Ramasesha, S, Pati, Swapan K, Krishnamurthy, HR, Shuai, Z, Bredas, JL
We extend the density-matrix renormalization-group DMRG method to exploit parity, $C_2$ (rotation by \pi), and electron-hole symmetries of model Hamiltonians. We demonstrate the power of this method...
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We develop a multiconfigurational symmetrized-projector quantum Monte Carlo MSPQMC method to calculate excited-state properties of Hubbard models. We compare the MSPQMC results for finite Hubbard...
Symmetrized projector quantum Monte Carlo studies of the ground state of $C_{60}$ (1996)
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
We develop a symmetrized version of the projector quantum Monte Carlo SPQMC method which preserves the symmetries of the system by simultaneously sampling all symmetry-related Ising configurations at...
Variational Monte Carlo and Configuration Interaction Studies of $C_{60}$ and Its Fragments (1996)
Srinivasan, Bhargavi, Ramasesha, S, Krishnamurthy, HR
The $C_{60}$ molecule and its fragments are studied using configuration interaction and variational Monte Carlo techniques, within the Hubbard model. Using benzene as a test case, we compare the...
Ray, Paresh Chandra, Das, Puspendu Kumar, Ramasesha, S
Dynamic and static first hyperpolarizabilities $(\beta)$ of a series of benzoic and cinnamic acids in water have been investigated. These acids exist in a mixture of acidic and basic forms in...
Phase Diagram of the Spin-One Heisenberg System with Dimerization and Frustration (1995)
Pati, Swapan, Chitra, R., Sen, Diptiman, Krishnamurthy, H. R., Ramasesha, S.
We use the density matrix renormalization group method to study the ground state properties of an antiferromagnetic spin-$1$ chain with a next-nearest neighbor exchange $J_2 ~$ and an alternation...
A New Mechanism For Ferromagnetism In C-60-TDAE (1995)
Based on the topology of C-60 and the resulting non-disjoint nature of the lowest unoccupied molecular orbitals, Ne propose a new model for ferromagnetic exchange in C-60-TDAE. Within the Hubbard...
DMRG Studies of the Spin-Half Heisenberg System with Dimerization and Frustration (1994)
Chitra, R., Pati, Swapan K., Krishnamurthy, H. R., Sen, D., Ramasesha, S.
Using the density matrix renormalization group technique, we study the ground state phase diagram and other low-energy properties of an isotropic antiferromagnetic spin-half chain with both...
Nature of exchange interactions in stacked radicals/radical-ions of cyclic polyenes (1994)
Ramasesha, S, Sinha, B, Albert, IDL
From full configuration interaction calculations on stacked cyclic polyene radicals/radical-ions, within the Hubbard and the Pariser-Parr-Pople models, we show that the ground state is not always a...
Nature of exchange interactions in stacked radicals/radical-ions of cyclic polyenes (1994)
Ramasesha, S, Sinha, B, Albert, IDL
From full configuration interaction calculations on stacked cyclic polyene radicals/radical-ions, within the Hubbard and the Pariser-Parr-Pople models, we show that the ground state is not always a...
Optical nonlinearities in symmetric cyanine dyes and related systems (1993)
Albert, IDL, Das, PK, Ramasesha, S
First- and third-order dynamic polarizabilities and hyperpolarizabilities of aza-cyanine and symmetric cyanine dyes have been computed exactly within the correlated Pariser-Parr-Pople model defined...
Optical nonlinearities in symmetric cyanine dyes and related systems (1993)
Albert, IDL, Das, PK, Ramasesha, S
First- and third-order dynamic polarizabilities and hyperpolarizabilities of aza-cyanine and symmetric cyanine dyes have been computed exactly within the correlated Pariser-Parr-Pople model defined...
Second- and third-order dynamic polarizabilities related to the Pockels and Kerr coefficients of polyenes and substituted polyenes have been computed exactly for a Pariser-Parr-Pople model. It is...
Electronic structure of high-$T_c$ superconductors and related compounds (1992)
Sarma, DD, Krishnamurthy, HR, Nimkar, S, Ramasesha, S, Mitra, PP, Ramakrishnan, TV
The authors study a 5-band Hubbard model for the $CuO_2$ planes in cuprate superconductors using Hartree-Fock mean-field theory including spiral spin density waves. For the half-filled case they...
Second- and third-order dynamic polarizabilities related to the Pockels and Kerr coefficients of polyenes and substituted polyenes have been computed exactly for a Pariser-Parr-Pople model. It is...
Electronic structure of high-$T_c$ superconductors and related compounds (1992)
Sarma, DD, Krishnamurthy, HR, Nimkar, S, Ramasesha, S, Mitra, PP, Ramakrishnan, TV
The authors study a 5-band Hubbard model for the $CuO_2$ planes in cuprate superconductors using Hartree-Fock mean-field theory including spiral spin density waves. For the half-filled case they...
We have obtained the model exact static polarizability of the $Cu_4O_8$ cluster within the three-band Hubbard model for different doping levels. The excitation gaps as well as the weight of the $O^-$...
Role of $\sigma-\pi$ interactions on linear and nonlinear susceptibilities in polyenes (1991)
The validity of the $\sigma-\pi$ separability approximation has been well established for some properties of the low-lying states in long polyenes. However, properties such as polarizabilities and...
Sinha, Bhabadyuti, Ramasesha, S
The different spin states in pseudo-ortho-, pseudo-meta- and pseudo-para-dicarbene substituted [2,2]-paracyclophanes have been studied using a Heisenberg spin model. The ground state is always a...
Theoretical study of spin interactions in stacked acetylene radical ions (1991)
Ramasesha, S, Sinha, Bhabadyuti
The search for organic ferromagnets has so far focused on radical ions of cyclic conjugated systems which have a doubly degenerate highest-occupied molecular orbital. However, recent theoretical...
Albert, IDL, Ramasesha, S, Das, PK
Polymethineimines (PMI's) and poly(2,3-diazabutadienes)(PBD's) are isoelectronic with polyacetylenes (PA's), but they do not possess the electron-hole or the spatial symmetries of PA. While PMI has...
Second-harmonic generation and electronic structure of polymethineimines: a theoretical study (1991)
Albert, IDL, Das, Puspendu K, Ramasesha, S
The second-harmonic-generation (SHG) coefficients and properties of low-lying electronic states in polyrnethineimines $(-CH=N-)_x$, up to x= 5 are calculated exactly within the PPP...
We have obtained the model exact static polarizability of the $Cu_4O_8$ cluster within the three-band Hubbard model for different doping levels. The excitation gaps as well as the weight of the $O^-$...
Theoretical study of spin interactions in stacked acetylene radical ions (1991)
Ramasesha, S, Sinha, Bhabadyuti
The search for organic ferromagnets has so far focused on radical ions of cyclic conjugated systems which have a doubly degenerate highest-occupied molecular orbital. However, recent theoretical...
Second-harmonic generation and electronic structure of polymethineimines: a theoretical study (1991)
Albert, IDL, Das, Puspendu K, Ramasesha, S
The second-harmonic-generation (SHG) coefficients and properties of low-lying electronic states in polyrnethineimines $(-CH=N-)_x$, up to x= 5 are calculated exactly within the PPP...
Role of $\sigma-\pi$ interactions on linear and nonlinear susceptibilities in polyenes (1991)
The validity of the $\sigma-\pi$ separability approximation has been well established for some properties of the low-lying states in long polyenes. However, properties such as polarizabilities and...
Sinha, Bhabadyuti, Ramasesha, S
The different spin states in pseudo-ortho-, pseudo-meta- and pseudo-para-dicarbene substituted [2,2]-paracyclophanes have been studied using a Heisenberg spin model. The ground state is always a...
Albert, IDL, Ramasesha, S, Das, PK
Polymethineimines (PMI's) and poly(2,3-diazabutadienes)(PBD's) are isoelectronic with polyacetylenes (PA's), but they do not possess the electron-hole or the spatial symmetries of PA. While PMI has...
Stability of the high-spin ground state in alternant $\pi$-conjugated organic molecules (1990)
Sinha, Bhabadyuti, Albert, IDL, Ramasesha, S
Alternant quantum cell models with unequal numbers of atoms on the two sublattices have been predicted to have a high-spin ground state. In this paper, we examine the stability of this high-spin...
We report model exact electric-field-induced second-harmonic- (EFISH) generation coefficients of polyene systems, within the Pariser-Parr-Pople model. For a given unsubstituted polyene, we find that...
Second harmonic generation coefficients in push-pull polyenes:a model exact study (1990)
The correlated Pariser-Parr-Pople (PPP) model for interacting $\pi$ electrons is employed for calculating the model exact SHG coefficients $(\beta^{exact})$ of push-pull polyenes with 4 to 10 carbon...
Sudden Polarization in Push-Pull Polyenes: A Model Exact Study (1990)
In substituted polyenes, it has been conjectured that a large charge separation occurs when a rotation of $90^o$ is carried out about a double bond. In this paper, using a model exact solution of the...
A model exact calculation of SHG coefficients in polysubstituted push-pull polyenes (1990)
Albert, IDL, Das, Puspendu K, Ramasesha, S
We report the model exact second-harmonic generation coefficients $(\beta^{exact})$ in polysubstituted all-trans push—pull polyenes up to ten carbon atoms. The Pariser-Parr-Pople (PPP) model with...
Sudden polarization in interacting model $\pi$ systems: An exact study (1990)
The twisted excited state of polyenes has attracted much theoretical and experimental attention due to the postulate that it exhibits sudden polarization for twist angle $\theta = 90^°$. We examine...
A new algorithm for solving large inhomogeneous linear system of algebraic equations (1990)
An algorithm based on a small matrix approach to the solution of a system of inhomogeneous linear algebraic equations is developed and tested in this short communication. The solution is assumed to...
Sudden Polarization in Push-Pull Polyenes: A Model Exact Study (1990)
In substituted polyenes, it has been conjectured that a large charge separation occurs when a rotation of $90^o$ is carried out about a double bond. In this paper, using a model exact solution of the...
Second harmonic generation coefficients in push-pull polyenes:a model exact study (1990)
The correlated Pariser-Parr-Pople (PPP) model for interacting $\pi$ electrons is employed for calculating the model exact SHG coefficients $(\beta^{exact})$ of push-pull polyenes with 4 to 10 carbon...
Sudden polarization in interacting model $\pi$ systems: An exact study (1990)
The twisted excited state of polyenes has attracted much theoretical and experimental attention due to the postulate that it exhibits sudden polarization for twist angle $\theta = 90^°$. We examine...
Stability of the high-spin ground state in alternant $\pi$-conjugated organic molecules (1990)
Sinha, Bhabadyuti, Albert, IDL, Ramasesha, S
Alternant quantum cell models with unequal numbers of atoms on the two sublattices have been predicted to have a high-spin ground state. In this paper, we examine the stability of this high-spin...
We report model exact electric-field-induced second-harmonic- (EFISH) generation coefficients of polyene systems, within the Pariser-Parr-Pople model. For a given unsubstituted polyene, we find that...
A model exact calculation of SHG coefficients in polysubstituted push-pull polyenes (1990)
Albert, IDL, Das, Puspendu K, Ramasesha, S
We report the model exact second-harmonic generation coefficients $(\beta^{exact})$ in polysubstituted all-trans push—pull polyenes up to ten carbon atoms. The Pariser-Parr-Pople (PPP) model with...
A new algorithm for solving large inhomogeneous linear system of algebraic equations (1990)
An algorithm based on a small matrix approach to the solution of a system of inhomogeneous linear algebraic equations is developed and tested in this short communication. The solution is assumed to...
Organic Superconductivity: An Experiment Based Theory (1988)
Within the last decade the superconducting critical temperature in the organics has gone up from about 1K to greater than 10K, but the search for a comprehensive theory is still on. A completely...
Organic Superconductivity: An Experiment Based Theory (1988)
Within the last decade the superconducting critical temperature in the organics has gone up from about 1K to greater than 10K, but the search for a comprehensive theory is still on. A completely...
Estimation of Correlation Energy and the Exchange Constant in Yttrium Barium Copper Oxides (1987)
The Hubbard on-site correlation energy U and the transfer energy t for the electron hop between the copper $d_{x^2-y^2}$ and the overlapping p orbital of the nearest-neighbour oxygen atom are...
Static Spin Correlations in Singlet States via Triplet Overlap Integrals (1987)
An effcient method for the calculation of static spin-spin correlation matrix elements between singlet states is described. The method uses the property that the site spin operators $S_p^2$; converts...
Estimation of Correlation Energy and the Exchange Constant in Yttrium Barium Copper Oxides (1987)
The Hubbard on-site correlation energy U and the transfer energy t for the electron hop between the copper $d_{x^2-y^2}$ and the overlapping p orbital of the nearest-neighbour oxygen atom are...
Static Spin Correlations in Singlet States via Triplet Overlap Integrals (1987)
An effcient method for the calculation of static spin-spin correlation matrix elements between singlet states is described. The method uses the property that the site spin operators $S_p^2$; converts...
A diagrammatic valence bond method based on Rumer-Pauling rules for configuration interaction calculations is described. The advantages of this method are that it is simple and flexible and is...
Electron-electron interactions in polyacetylene (1986)
Experimental evidence for strong electron-electron interactions in polyacetylene is presented. These include (i) observation of a dipole forbidden state below the optical gap, (ii) observation of...
A diagrammatic valence bond method based on Rumer-Pauling rules for configuration interaction calculations is described. The advantages of this method are that it is simple and flexible and is...
An explanation of the phenomenon of polytypism (1984)
Based on the analogy between polytypes and spin-half Ising chains, polytypes can be considered as different phases of a spin-half Ising system with competing nearest neighbour and next nearest...
An explanation of the phenomenon of polytypism (1984)
Based on the analogy between polytypes and spin-half Ising chains, polytypes can be considered as different phases of a spin-half Ising system with competing nearest neighbour and next nearest...
Computer simulation of polytypes (1980)
Uppal, MK, Ramasesha, S, Rao, CNR
Polytypes have been simulated, treating them as analogues of a one-dimensional spin-half Ising chain with competing short-range and infinite-range interactions. Short-range interactions are treated...