Electrical conductivity of high-pressure liquid hydrogen by quantum Monte Carlo methods (2009)
Lin, Fei, Morales, Miguel A., Delaney, Kris T., Pierleoni, Carlo, Martin, Richard M., Ceperley, D. M.
We compute the electrical conductivity for liquid hydrogen at high pressure using quantum Monte Carlo. The method uses Coupled Electron-Ion Monte Carlo to generate configurations of liquid hydrogen....
Collin, Simon M, Metcalfe, Chris, Zuccolo, Luisa, Lewis, Sarah J, Chen, Lina, Cox, Angela, ...
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Thomas, Kate, Rafiq, Sajjad, Frayling, Timothy M., Ebrahim, Shah, Kumari, Meena, Gallacher, John, ...
Background Levels of the proinflammatory cytokine interleukin-18 (IL-18) are raised in old age and are associated with reduced physical functioning. Previous studies have indicated that the C allele...
On the Origin of the 2DEG Carrier Density at the LaAlO$_3$/SrTiO$_3$ Interface (2008)
Popović, Zoran S., Satpathy, Sashi, Martin, Richard M.
Transport measurements of the two-dimensional electron gas (2DEG) at the LaAlO$_3$/SrTiO$_3$ interface have found a density of carriers much lower than expected from the "polar catastrophe"...
Spin resolved energy parametrization of a quasi-one-dimensional electron gas (2008)
Shulenburger, Luke, Casula, Michele, Senatore, Gaetano, Martin, Richard M.
By carrying out extensive lattice regularized diffusion Monte Carlo calculations, we study the spin and density dependence of the ground state energy for a quasi-one-dimensional electron gas, with...
Molecular hydrogen adsorbed on benzene: insights from a quantum Monte Carlo study (2008)
Beaudet, Todd D., Casula, Michele, Kim, Jeongnim, Sorella, Sandro, Martin, Richard M.
We present a quantum Monte Carlo study of the hydrogen-benzene system where binding is very weak. We demonstrate that the binding is well described at both variational Monte Carlo (VMC) and diffusion...
Renormalization factor and effective mass of the two-dimensional electron gas (2008)
Holzmann, Markus, Bernu, Bernard, Olevano, Valerio, Martin, Richard M., Ceperley, David M.
We calculate the momentum distribution of the Fermi liquid phase of the homogeneous, two-dimensional electron gas. We show that, close to the Fermi surface, the momentum distribution of a finite...
Molecular hydrogen adsorbed on benzene: insights from a quantum Monte Carlo study (2008)
Beaudet, Todd D., Casula, Michele, Kim, Jeongnim, Sorella, Sandro, Martin, Richard M.
We present a quantum Monte Carlo study of the hydrogen-benzene system where binding is very weak. We demonstrate that the binding is well described at both variational Monte Carlo (VMC) and diffusion...
Efficient method to calculate total energies of large nanoclusters (2008)
Yu, M., Ramprasad, R., Fernando, G. W., Martin, Richard M.
We present an approach to calculate total energies of nanoclusters based on first principles estimates. For very large clusters the total energy can be separated into surface, edge and corner...
Screening of a Point Charge: A Fixed-Node Diffusion Monte Carlo Study (2007)
Erik Koch, Olle Gunnarsson, Richard M. Martin
. We study the static screening in a Hubbard-like model using fixed-node diffusion Monte Carlo. We find that the random phase approximation is surprisingly accurate even for metallic systems close to...
Density-Functional Study of the Hydrogen-Bonded Water Cluster H 5 O (2007)
Yong-hoon Kim, In-ho Lee, Richard M. Martin
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Humphreys, Vikki, Martin, Richard M., Ratcliffe, Brian, Duthie, Susan, Wood, Sharon, Gunnell, David, ...
Background One commonly held theory of ageing is that it is caused by oxidative damage to critical molecules in the body, including proteins, lipids and nucleic acids. Accumulation of oxidative DNA...
Disorder Enhanced Spin Polarization in Diluted Magnetic Semiconductors (2007)
Lee, Byounghak, Cartoixa, Xavier, Trivedi, Nandini, Martin, Richard M.
We present a theoretical study of diluted magnetic semiconductors that includes spin-orbit coupling within a realistic host band structure and treats explicitly the effects of disorder due to...
The Finite Size Error in Many-body Simulations with long-Ranged Interactions (2006)
Chiesa, Simone, Ceperley, David M., Martin, Richard M., Holzmann, Markus
We discuss the origin of the finite size error of the energy in many-body simulation of systems of charged particles and we propose a correction based on the random phase approximation at long wave...
The Finite Size Error in Many-body Simulations with long-Ranged Interactions (2006)
Chiesa, Simone, Ceperley, David M., Martin, Richard M., Holzmann, Markus
We discuss the origin of the finite size error of the energy in many-body simulation of systems of charged particles and we propose a correction based on the random phase approximation at long wave...
The Finite Size Error in Many-body Simulations with long-Ranged Interactions (2006)
Chiesa, Simone, Ceperley, David M., Martin, Richard M., Holzmann, Markus
We discuss the origin of the finite size error of the energy in many-body simulation of systems of charged particles and we propose a correction based on the random phase approximation at long wave...
The Finite Size Error in Many-body Simulations with long-Ranged Interactions (2006)
Chiesa, Simone, Ceperley, David M., Martin, Richard M., Holzmann, Markus
We discuss the origin of the finite size error of the energy in many-body simulation of systems of charged particles and we propose a correction based on the random phase approximation at long wave...
Role of the spin-orbit splitting and the dynamical fluctuations in the Si(557)-Au surface (2005)
Sanchez-Portal, Daniel, Riikonen, Sampsa, MArtin, Richard M.
Our it ab initio calculations show that spin-orbit coupling is crucial to understand the electronic structure of the Si(557)-Au surface. The spin-orbit splitting produces the two one-dimensional...
Martin, Richard M., Gunnell, David, Davey Smith, George
The influence of breastfeeding on blood pressure in later life is uncertain. The authors conducted a systematic review of published studies from which estimates of a mean difference (standard error)...
Martin, Richard M., Gunnell, David, Pemberton, John, Watson, Simone, Frankel, Stephen, Davey Smith, George
Martin, Richard M, Gunnell, David, Pemberton, John, Watson, Simone, Frankel, Stephen, Davey Smith, George
Jahn-Teller Distortion and Ferromagnetism in the Dilute Magnetic Semiconductors GaN:Mn (2004)
Using first-principles total-energy methods, we investigate Jahn-Teller distortions in III-V dilute magnetic semiconductors, GaAs:Mn and GaN:Mn in the cubic zinc blende structure. The results for an...
Spin-Orbit Effects in Diluted Magnetic Semiconductors (2004)
Lee, Byounghak, Cartoixa, Xavier, Trivedi, Nandini, Martin, Richard M.
We present a theoretical study of diluted magnetic semiconductors that treats the local sp-d exchange interaction J between the itinerant carriers and the Mn d electrons within a realistic band...
Electron-Phonon Interactions in C$_{28}$-derived Molecular Solids (2004)
Romero, Nichols A., Kim, Jeongnim, Martin, Richard M.
We present {\it ab initio} density-functional calculations of molecular solids formed from C$_{28}$-derived closed-shell fullerenes. Solid C$_{28}$H$_4$ is found to bind weakly and exhibits many of...
Martin, Richard M, Davey Smith, George, Mangtani, Punam, Tilling, Kate, Frankel, Stephen, Gunnell, David
Aims To investigate the association of breastfeeding with all-cause, cardiovascular, and ischaemic heart disease mortality. Methods and results A long-term follow-up of 4999 children originally...
First principles study of the Si(557)-Au surface (2002)
Sanchez-Portal, Daniel, Martin, Richard M.
We have performed a density functional study of fifteen different structural models of the Si(557)-Au surface reconstruction. Here we present a brief summary of the main structural trends obtained...
Tsolakidis, Argyrios, Sanchez-Portal, Daniel, Martin, Richard M.
We report on a general method for the calculation of the frequency-dependent optical response of clusters based upon time-dependent density functional theory (TDDFT). The implementation is done using...
Bonding, Moment Formation, and Magnetic Interactions in Ca14MnBi11 and Ba14MnBi11 (2001)
Sanchez-Portal, D., Martin, Richard M., Kauzlarich, S. M., Pickett, W. E.
The ``14-1-11'' phase compounds based on magnetic Mn ions and typified by Ca14MnBi11 and Ba14MnBi11 show unusual magnetic behavior, but the large number (104) of atoms in the primitive cell has...
Two distinct metallic bands associated with monatomic Au wires on the Si(557)-Au surface (2001)
Sanchez-Portal, Daniel, Gale, Julian D., Garcia, Alberto, Martin, Richard M.
The Si(557)-Au surface, containing monatomic Au wires parallel to the steps, has been proposed as an experimental realization of an ideal one-dimensional metal. In fact, recent photoemission...
First principles study of the adsorption of C60 on Si(111) (2000)
Sanchez-Portal, Daniel, Artacho, Emilio, Pascual, J. I., Gomez-Herrero, J., Martin, Richard M., Soler, Jose M.
The adsorption of C60 on Si(111) has been studied by means of first-principles density functional calculations. A 2x2 adatom surface reconstruction was used to simulate the terraces of the 7x7...
A quantum Monte Carlo study of the one-dimensional ionic Hubbard model (2000)
Wilkens, Tim, Martin, Richard M.
Quantum Monte Carlo methods are used to study a quantum phase transition in a 1D Hubbard model with a staggered ionic potential (D). Using recently formulated methods, the electronic polarization and...
Souza, Ivo, Martin, Richard M., Marzari, Nicola, Zhao, Xinyuan, Vanderbilt, David
We have constructed maximally-localized Wannier functions for prototype structures of solid molecular hydrogen under pressure, starting from LDA and tight-binding Bloch wave functions. Each occupied...
Shumway, J., Fonseca, L. R. C., Leburton, J. P., Martin, Richard M., Ceperley, D. M.
We have calculated the exchange, correlation, and total electronic energy of a realistic InAs self-assembled quantum dot embedded in a GaAs matrix as a function of the number of electrons in the dot....
Metallization of molecular hydrogen (2000)
Staedele, Martin, Martin, Richard M.
We study metallization of molecular hydrogen under pressure using exact exchange (EXX) Kohn-Sham density-functional theory in order to avoid well-known underestimates of band gaps associated with...
Metal-Insulator transitions in generalized Hubbard models (1999)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
We study the Mott transition in Hubbard models with a degenerate band on different 3-dimensional lattices. While for a non-degenerate band only the half-filled system may exhibit a Mott transition,...
Object-oriented construction of a multigrid electronic-structure code with Fortran 90 (1999)
Kim, Yong-Hoon, Lee, In-Ho, Martin, Richard M.
We describe the object-oriented implementation of a higher-order finite-difference density-functional code in Fortran 90. Object-oriented models of grid and related objects are constructed and...
Kim, Yong-Hoon, Lee, In-Ho, Nagaraja, Satyadev, Leburton, Jean-Pierre, Hood, Randolph Q., Martin, Richard M.
We investigate the behavior of three-dimensional (3D) exchange-correlation energy functional approximations of density functional theory in anisotropic systems with two-dimensional (2D) character....
Polarization and localization in insulators: generating function approach (1999)
Souza, Ivo, Wilkens, Tim, Martin, Richard M.
We develop the theory and practical expressions for the full quantum-mechanical distribution of the intrinsic macroscopic polarization of an insulator in terms of the ground state wavefunction. The...
Density-functional Study of Small Molecules within the Krieger-Li-Iafrate Approximation (1999)
Kim, Yong-Hoon, Städele, Martin, Martin, Richard M.
We report density-functional studies of several small molecules ($H_{2}, N_{2}, CO, H_{2}O$, and $CH_{4}$) within the Krieger-Li-Iafrate (KLI) approximation to the exact Kohn-Sham local exchange...
Filling dependence of the Mott transition in the degenerate Hubbard model (1999)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
Describing the doped Fullerenes using a generalized Hubbard model, we study the Mott transition for different integer fillings of the t_1u band. We use the opening of the energy-gap E_g as a...
Screening of a point charge: a fixed-node diffusion Monte Carlo study (1999)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
We study the static screening in a Hubbard-like model using fixed-node diffusion Monte Carlo. We find that the random phase approximation is surprisingly accurate even for metallic systems close to...
Optimization of Gutzwiller Wavefunctions in Quantum Monte Carlo (1999)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
Gutzwiller functions are popular variational wavefunctions for correlated electrons in Hubbard models. Following the variational principle, we are interested in the Gutzwiller parameters that...
Screening, Coulomb pseudopotential, and superconductivity in alkali-doped Fullerenes (1999)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
We study the static screening in a Hubbard-like model using quantum Monte Carlo. We find that the random phase approximation is surprisingly accurate almost up to the Mott transition. We argue that...
THE PSEUDOHARMONIC THEORY OF LATTICE VIBRATIONS, (1998)
Cohen,Morrel H., Martin,Richard M.
A self-consistent harmonic hamiltonian is derived to describe lattice vibrations in an anharmonic crystal. The force constants are shown to be both self-consistent averages of derivatives of the...
MICROSCOPIC THEORY OF FORCE CONSTANTS IN SOLIDS, (1998)
Cohen,Morrel H., Martin,Richard M., Pick,Robert M.
The expression of the force constants are derived from the energy of a neutral system of interacting nuclei and electrons. Those force constants depend only on the nuclear charges and the inverse...
Atomic Arrangements and Electronic Properties of Semiconductor Surfaces and Interfaces. (1998)
Chadi,D. J., Martin,Richard M.
The areas of research during the past 12 months have included: step-formation energies and domain orientation at Si(111) surfaces; the electronic structure of the Al-GaAs(110) surface chemisorption...
Polarization and Strong Infra-Red Activity in Compressed Solid Hydrogen (1998)
Souza, Ivo, Martin, Richard M.
Under a pressure of ~150 GPa solid molecular hydrogen undergoes a phase transition accompanied by a dramatic rise in infra-red absorption in the vibron frequency range. We use the Berry's phase...
Fixed-node DMC for Fermions on a lattice: Application to the doped Fullerides (1998)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
Fullerides are crystals made from C60 molecules. When doped with alkali metals the valence electrons of the alkali atoms are transfered to the C60 molecules. We show how to set up a model Hamiltonian...
Dielectric screening in doped Fullerides (1998)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
For conventional superconductors the electron-electron interaction is strongly reduced by retardation effects, making the formation of Cooper pairs possible. In the alkali-doped Fullerides, however,...
Quantum Monte Carlo calculations for integer-doped Fullerides (1998)
Koch, Erik, Gunnarsson, Olle, Martin, Richard M.
The doped Fullerides can be well described by a Hubbard model, which comprises the partly filled, threefold-degenerate t_1u orbital and the on-site Coulomb interaction U. The orbital degeneracy is...
Kwon, Yongkyung, Ceperley, D. M., Martin, Richard M.
The correlation energy of the homogeneous three-dimensional interacting electron gas is calculated using the variational and fixed-node diffusion Monte Carlo methods, with trial functions that...
Electronic Structure Calculations Using An Adaptive Wavelet Basis (1998)
D. A. Richie, P. Von Allmen, K. Hess, Richard M. Martin
The use of a wavelet basis can lead to efficient methods for performing ab initio electronic structure calculations of inherently localized structures. In this work wavelets are used to construct an...
Ortiz, Gerardo, Souza, Ivo, Martin, Richard M.
We present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is...
Mott-Hubbard insulators for systems with orbital degeneracy (1997)
Gunnarsson, Olle, Koch, Erik, Martin, Richard M.
We study how the electron hopping reduces the Mott-Hubbard band gap in the limit of a large Coulomb interaction U and as a function of the orbital degeneracy N. The results support the conclusion...
Microscopic Functional Theory of Dielectrics (1997)
Richard M. Martin, Gerardo Ortiz
Density functional theory (DFT) rests upon the proofs by Hohenberg and Kohn, which show that all properties of quantum many-body systems are functionals of the ground state density, and the Kohn-Sham...
Mott Transition in Degenerate Hubbard Models: Application to Doped Fullerenes (1996)
Gunnarsson, Olle, Koch, Erik, Martin, Richard M.
The Mott-Hubbard transition is studied for a Hubbard model with orbital degeneracy N, using a diffusion Monte-Carlo method. Based on general arguments, we conjecture that the Mott-Hubbard transition...
NHS waiting lists and evidence of national or local failure: analysis of health service data
Martin, Richard M, Sterne, Jonathan A C, Gunnell, David, Ebrahim, Shah, Davey Smith, George, Frankel, Stephen
NHS waiting lists and evidence of national or local failure: analysis of health service data
Martin, Richard M, Sterne, Jonathan A C, Gunnell, David, Ebrahim, Shah, Davey Smith, George, Frankel, Stephen
Wheeler, Benedict W, Gunnell, David, Metcalfe, Chris, Stephens, Peter, Martin, Richard M
Objective To investigate the population impact on the incidence of suicide and non-fatal self harm of regulatory action in 2003 to restrict the use of selective serotonin reuptake inhibitors (SSRIs)...
The Effects on Stature of Poverty, Family Size and Birth Order: British Children in the 1930s
Timothy J. Hatton, Richard M. Martin
This paper examines effects of socio-economic conditions on the standardised heights and body mass index of children in Interwar Britain. It uses the Boyd Orr cohort, a survey of predominantly poor...
Wood, Lesley, Egger, Matthias, Gluud, Lise Lotte, Schulz, Kenneth F, Jüni, Peter, Altman, Douglas G, ...
Objective To examine whether the association of inadequate or unclear allocation concealment and lack of blinding with biased estimates of intervention effects varies with the nature of the...
A clinical model for decision-making
Richard Martin's aim in this paper is to present a critical method of making ethical decisions in a medical context. He feels that such a reflective method provides the best means of making the...
Childhood Economic Conditions and Length of Life: Evidence from the UK Boyd Orr Cohort, 1937-2005
Paul Frijters, Michael A. Shields, Timothy J. Hatton, Richard M. Martin
We study the importance of childhood socioeconomic conditions in explaining differences in life expectancy using data from a sample of around 5,000 children collected in the UK in 1937-39, who have...
The Effects on Stature of Poverty, Family Size and Birth Order: British Children in the 1930s
Hatton, Timothy J., Martin, Richard M.
This paper examines effects of socio-economic conditions on the standardised heights and body mass index of children in Interwar Britain. It uses the Boyd Orr cohort, a survey of predominantly poor...
Fertility Decline and the Heights of Children in Britain, 1886-1938
Hatton, Timothy J., Martin, Richard M.
In this paper we argue that the fertility decline that began around 1880 had substantial positive effects on the health of children, as the quality-quantity trade-off would suggest. We use microdata...
The double jeopardy of clustered measurement and cluster randomisation
Kramer, Michael S, Martin, Richard M, Sterne, Jonathan A C, Shapiro, Stanley, Dahhou, Mourad, Platt, Robert W
Michael S Kramer and colleagues suggest that double clustering might explain the negative results of some cluster randomised trials and describe some strategies for avoiding the problem
Fertility Decline and the Heights of Children in Britain, 1886-1938
Timothy J. Hatton, Richard M. Martin
In this paper we argue that the fertility decline that began around 1880 had substantial positive effects on the health of children, as the quality-quantity trade-off would suggest. We use microdata...