University of Illinois Urbana-Champaign

A quantum Monte Carlo study of the high pressure phases of solid hydrogen

Natoli, Vincent Dominic

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Description

Title
A quantum Monte Carlo study of the high pressure phases of solid hydrogen
Author(s)
Natoli, Vincent Dominic
Issue Date
1994
Doctoral Committee Chair(s)
Martin, Richard M.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Diffusion Monte Carlo (DMC)
  • Variation Monte Carlo
  • computational physics
  • high pressure
  • high pressure phases
  • solid hydrogen
  • hydrogen
  • quantum physics
Language
en
Abstract
Variational and Diffusion Monte Carlo are powerful computational methods which can afford accurate estimates of the ground state properties of quantum many-body problems. We have applied these Monte Carlo methods to the high pressure phases of solid hydrogen to elucidate those parts of the phase diagram where experimental results are inconclusive or lacking. The method allows us to treat both electrons and protons as quantum particles by incorporating them in the trial wavefunction and avoids the Born-Oppenheimer and harmonic approximations. Our trial wavefunction uses single-body solutions from a meanfield calculation coupled with standard pair potential terms to achieve the most accurate results to date. Equally accurate results were realized for calculations in the disparate insulating molecular and metallic atomic regime. We performed a study of the possible ground state structures of the atomic metallic phase of hydrogen which identifies a new family of low energy atomic structures. Another study was done on the molecular phase over the range of pressures( 40-180GPa) where recent experiments have observed spectral discontinuities and other interesting new phenomena. Particular attention was directed to determining the equation of state and orientational ordering. We find that molecular hydrogen adopts a lower symmetry insulating structure over a wide range of pressure. The results of the atomic and molecular studies are combined to draw conclusions about the molecular-atomic transition and other details about the high pressure phase diagram.
Type of Resource
text
Permalink
http://hdl.handle.net/2142/18880
Copyright and License Information
1994 Vincent Dominic Natoli

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