Zobrazeno 1 - 10
of 386
pro vyhledávání: '"Needs, R. J."'
We present an overview of the variational and diffusion quantum Monte Carlo methods as implemented in the CASINO program. We particularly focus on developments made in the last decade, describing state-of-the-art quantum Monte Carlo algorithms and so
Externí odkaz:
http://arxiv.org/abs/2003.06506
Publikováno v:
Physical Review B 99, 064101 (2019)
Calcium silicate perovskite (CaSiO$_3$) is one of the major mineral components of the lower mantle, but has been the subject of relatively little work compared to the more abundant Mg-based materials. One of the major problems related to CaSiO$_3$ th
Externí odkaz:
http://arxiv.org/abs/1902.03828
Autor:
Prentice, Joseph C. A., Needs, R. J.
High-level vibrational calculations have been used to investigate anharmonicity in a wide variety of materials using density-functional-theory (DFT) methods. We have developed a new and efficient approach for describing strongly-anharmonic systems us
Externí odkaz:
http://arxiv.org/abs/1706.05387
Publikováno v:
Phys. Rev. B 95, 054118 (2017)
We investigate the high-pressure behaviour of beryllium, magnesium and calcium difluorides using ab initio random structure searching and density functional theory (DFT) calculations, over the pressure range 0-70 GPa. Beryllium fluoride exhibits exte
Externí odkaz:
http://arxiv.org/abs/1702.00746
Publikováno v:
Phys. Rev. B 95, 014108 (2017)
First-principles density functional theory methods are used to investigate the structure, energetics, and vibrational motions of the neutral vacancy defect in diamond. The measured optical absorption spectrum demonstrates that the tetrahedral $T_d$ p
Externí odkaz:
http://arxiv.org/abs/1701.01118
Publikováno v:
Phys. Rev. B 95, 115116 (2017)
We use coupled-cluster quantum chemical methods to calculate the energetics of molecular clusters cut out of periodic molecular hydrogen structures that model observed phases of solid hydrogen. The hydrogen structures are obtained from Kohn-Sham dens
Externí odkaz:
http://arxiv.org/abs/1611.00371
Publikováno v:
Phys. Rev. B 94, 165170 (2016)
We report a systematic analysis of the performance of a widely used set of Dirac-Fock pseudopotentials for quantum Monte Carlo (QMC) calculations. We study each atom in the periodic table from hydrogen (Z=1) to mercury (Z=80), with the exception of t
Externí odkaz:
http://arxiv.org/abs/1607.01544
Publikováno v:
Physical Review A 93, 042702 (2016)
We propose a smooth pseudopotential for the contact interaction acting between ultracold atoms confined to two dimensions. The pseudopotential reproduces the scattering properties of the repulsive contact interaction up to 200 times more accurately t
Externí odkaz:
http://arxiv.org/abs/1603.05001
We have used density-functional-theory methods and the ab initio random structure searching (AIRSS) approach to predict stable structures and stoichiometries of mixtures of iron and oxygen at high pressures. Searching was performed for 12 different s
Externí odkaz:
http://arxiv.org/abs/1508.05247
Autor:
Drummond, N. D., Monserrat, Bartomeu, Lloyd-Williams, Jonathan H., Rios, P. Lopez, Pickard, Chris J., Needs, R. J.
Publikováno v:
Nature Communications 6, 7794 (2015)
Establishing the phase diagram of hydrogen is a major challenge for experimental and theoretical physics. Experiment alone cannot establish the atomic structure of solid hydrogen at high pressure, because hydrogen scatters X-rays only weakly. Instead
Externí odkaz:
http://arxiv.org/abs/1508.02313