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Quantum monte carlo methods for constrained systems
Author(s) -
Wolf Sarah,
Curotto Emanuele,
Mella Massimo
Publication year - 2014
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.24647
Subject(s) - quantum monte carlo , monte carlo method , diffusion monte carlo , statistical physics , ground state , propane , quantum , rotational energy , state vector , degrees of freedom (physics and chemistry) , physics , monte carlo molecular modeling , mathematics , classical mechanics , quantum mechanics , thermodynamics , markov chain monte carlo , statistics
The torsional ground state for ethane, the torsional, rotational, and mixed torsional and rotational ground state of propane are computed with a version of diffusion Monte Carlo adapted to handle the geometric complexity of curved spaces such as the Ramachandra space. The quantum NVT ensemble average for the mixed torsional and rotational degrees of freedom of propane is computed, using a version of Monte Carlo path integral, also adapted to handle curved spaces. These three problems are selected to demonstrate the generality and the applicability of the approaches described. The spaces of coordinates can be best constructed from the parameters of continuous Lie groups, and alternative methods based on vector spaces, where extended Lagrangian terms would be too cumbersome to implement. We note that the geometric coupling between the torsions and the rotations of propane produces a substantial effect on the ground state energy of propane, and that the quantum effects on the energy of propane are quite large even well above room temperature. © 2014 Wiley Periodicals, Inc.