The electronic spectrum of the UO2 molecule (2005)
Gagliardi, L, Heaven, MC, Krogh, JW, Roos, BO
The electronic spectrum of the UO2 Molecule has been determined using multiconfigurational wave functions together with the inclusion spin-orbit coupling. The molecule has been found to have a...
Hagberg, D, Karlstrom, G, Roos, BO, Gagliardi, L
The coordination environment of uranyl in water has been studied using a combined quantum mechanical and molecular dynamics approach. Multiconfigurational wave function calculations have been...
Coupled cluster methods are compared to multiconfigurational second-order perturbation theory in a study of the high spin d(x)s(2) -> d(x+1)s(1) excitations in first, second, and third row...
New relativistic ANO basis sets for transition metal atoms (2005)
Roos, BO, Lindh, R, Malmqvist, PA, Veryazov, V, Widmark, PO
New basis sets of the atomic natural orbital (ANO) type have been developed for the first, second, and third row transition metal atoms. The ANOs have been obtained from the average density matrix of...
A very short uranium-uranium bond: The predicted metastable U-2(2+) (2005)
Gagliardi, L, Pyykko, P, Roos, BO
Quantum chemical calculations, based on multiconfigurational wave functions and including relativistic effects, show that the U-2(2+) system has a large number of low-lying electronic states with S...
New relativistic ANO basis sets for actinide atoms (2005)
Roos, BO, Lindh, R, Malmqvist, PA, Veryazov, V, Widmark, PO
New basis sets of the atomic natural orbital (ANO) type have been developed for the actinide atoms Ac-Cm. The ANOs have been obtained from the average density matrix of the ground and lowest excited...
Theoretical study of PbO and the PbO anion (2005)
Ilias, M, Jensen, HJA, Kello, V, Roos, BO, Urban, M
PbO and PbO- were studied utilizing CCSD(T), CASSCF/CASPT2, and the Fock Space FSCCSD methods. Relativistic effects were treated by the spin-free, two-component infinite-order Douglas-Kroll-Hess,...
Barone, G, Silvestri, A, Roos, BO
The electronic structure and the UV- vis spectrum of reduced and oxidized model systems of the N, N'- 1,2phenylenebis( 2- mercapto- 2- methylpropionamide) copper complex have been studied using a...
Quantum chemical calculations show that the uranium molecule U-2 has a quintuple bond (2005)
Covalent bonding is commonly described by Lewis's theory(1), with an electron pair shared between two atoms constituting one full bond. Beginning with the valence bond description(2) for the hydrogen...
Collisional properties of trapped cold chromium atoms (2004)
Pavlovic, Z, Roos, BO, Côte, Renaud; U0051201, Sadeghpour, HR
We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to...
2MOLCAS as a development platform for quantum chemistry software (2004)
Veryazov, V, Widmark, PO, Serrano-Andres, L, Lindh, R, Roos, BO
This work presents the quantum chemistry package MOLCAS, with emphasis on its usefulness as a platform for developing new quantum chemical codes, and the reader is assumed to be familiar with such a...
Gusarov, S, Malmqvist, PA, Lindh, R, Roos, BO
A density functional theory based on a complete active space self consistent field (CASSCF) reference function with exact exchange is discussed. It is first shown that such a theory may be formulated...
Main group atoms and dimers studied with a new relativistic ANO basis set (2004)
Roos, BO, Lindh, R, Malmqvist, PA, Veryazov, V, Widmark, PO
New basis sets of the atomic natural orbital (ANO) type have been developed for the main group and rare gas atoms. The ANO's have been obtained from the average density matrix of the ground and...
Ghigo, G, Roos, BO, Stancil, PC, Weck, PF
Ab initio calculations of low-lying electronic states of CrH are presented, including potential energies, dipole and transition dipole moment (TDM) functions, and radiative lifetimes for X...
A theoretical study of the bonding in trivalent americium complexes (2004)
Vetere, V, Roos, BO, Maldivi, P, Adamo, C
An account of the electronic structure of AmF3 and AmCl3 has been obtained by Complete Active Space calculations (CASSCF and CASPT2) using either a scalar Douglas-Kroll-Hess Hamiltonian or a...
Ghigo, G, Roos, BO, Malmqvist, PA
A new shifted zeroth-order Hamiltonian is presented, which will be used in second-order multiconfigurational perturbation theory (CASPT2). The new approximation corrects for the systematic error of...
Relativistic quantum chemistry: the multiconfigurational approach (2004)
A multiconfigurational approach to the quantum chemistry of heavy element compounds is described. Relativistic effects are treated in two steps, both based on the Douglas-Kroll Hamiltonian. Scalar...
Are Hartree-Fock atoms too small or too large? (2004)
Cohen, AJ, Handy, NC, Roos, BO
We address the simple question, whether Hartree-Fock atoms are smaller or larger than exact (Schrodinger) atoms. As a measure, we use <r(2)>. We study the ground state of the atoms He-Kr. The...
Collisional properties of trapped cold chromium atoms (2004)
Pavlovic, Z, Roos, BO, Cote, R, Sadeghpour, HR
We report on calculations of the elastic cross section and thermalization rate for collision between two maximally spin-polarized chromium atoms in the cold and ultracold regimes, relevant to...
Roos, BO, Veryazov, V, Widmark, PO
New basis sets of the atomic natural orbital (ANO) type have been developed for the atoms Li-Fr and Be-Ra. The ANOs have been obtained from the average density matrix of the ground states and the...
Ground state structure of CuO2: a CASPT2 study (2001)
The ground state structure of CuO2, which has been discussed extensively in the literature, has been determined using a multiconfigurational SCF method and second-order perturbation theory. In the...
On the role of strain in blue copper proteins (2000)
Olsson, MHM, Roos, BO, De Kerpel, JOA
Theoretical investigations of the structure and function of the blue copper proteins are described. We have studied the optimum vacuum geometry of oxidised and reduced copper sites, the relative...
Ribbing, C, Gilliams, B, Ceulemans, Arnout; U0014297, Pierloot, Kristine; U0018862, Vandenbroucke, D, Roos, BO
A combined spectroscopic and theoretical investigation is devoted to the vibrational fine structure in the broad band spectrum at 4.2 K of the T-1(1g) and T-1(2g) states of Rh(III) d(6) doped in...
The role of the cysteine thiolate ligand for the unusual copper coordination geometry in the blue copper proteins has been studied by comparing the electronic structure, geometry, and energetics of a...
Relation between the structure and spectroscopic properties of blue copper proteins (1998)
De Kerpel, JOA, Ryde, U, Olsson, MHM, Roos, BO
The electronic spectra of three rhombic type I blue copper proteins, nitrite reductase, pseudoazurin, and cucumber basic protein, have been studied by ab initio multiconfigurational second-order...
Gilliams, B, Roos, BO, Karlstrom, G
The spin-orbit states of octahedral RhCl63- in the three lattices NaCl, Cs2NaYCl6 and water solution have been investigated theoretically with multiconfigurational self-consistent field (SCF) type...
Theoretical study of the structural and spectroscopic properties of stellacyanin (1998)
The electronic spectrum of the azurin Met121Gln mutant, a model of the blue copper protein stellacyanin, has been studied by ab initio multiconfigurational second-order perturbation theory (the...
Theoretical study of the electronic spectrum of plastocyanin (1997)
DeKerpel, JOA, Ryde, U, Roos, BO
The electronic spectrum of the blue copper protein plastocyanin has been studied by ab initio multiconfigurational second-order perturbation theory (the CASPT2 method). The six lowest electronic...
The cupric geometry of blue copper proteins is not strained (1996)
The geometry of several realistic models of the metal coordination sphere in the blue copper proteins has been optimised using high-level quantum chemical methods. The results show that the optimal...
Generally contracted Basis sets for the atoms H-Kr have been constructed using the atomic natural orbital (ANO) approach, with modifications for allowing symmetry breaking and state averaging. The...
Theoretical study of the chemical bonding in Ni(C2H4) and ferrocene (1995)
The equilibrium structure and bond energies of the transition-metal complexes Ni(C2H4) and ferrocene have been studied by using the complete active space (CAS)SCF method and second-order perturbation...
A theoretical study of the chemical bonding in M(CO)(x) (M=Cr, Fe, and Ni) (1994)
The equilibrium structure and bond energies of the transition metal complexes Ni(CO)(x) (x=1-4), Fe(CO)(5), and Cr(CO)(6) have been studied using the complete active space (CAS)SCF method and...
3p-3d intershell correlation-effects in transition-metal ions (1993)
The effect of 3p correlation on the relative term energies in the (3d)n configurations of first-row transition metal ions has been studied using CASSCF and multireference perturbation theory. It is...
Systematic ab-initio study of the ligand-field spectra of hexacyanometalate complexes (1993)
Van Praet, E, Vanquickenborne, LG, Roos, BO
The ground and ligand field excited states of the first-row hexacyanometalate complexes V(CN)64-, Cr(CN)63-, Mn(CN)63-,4-, Fe(CN)63-,4-, and Co(CN)63- have been studied using the complete active...