Quantum monte carlo methods for constrained systems
Article first published online: 28 FEB 2014
Copyright © 2014 Wiley Periodicals, Inc.
International Journal of Quantum Chemistry
Volume 114, Issue 10, pages 611–625, 15 May 2014
How to Cite
How to cite this article: Int. J. Quantum Chem. 2014, 114, 611–625. DOI: 10.1002/qua.24647, , .
- Issue published online: 1 APR 2014
- Article first published online: 28 FEB 2014
- Manuscript Accepted: 4 FEB 2014
- Manuscript Revised: 31 JAN 2014
- Manuscript Received: 19 NOV 2013
- ACS (Petroleum Research Fund). Grant Number: 48146-B6
- Università degli Studi dell'Insubria via the fund Fondi di Ateneo per la Ricerca (FAR)
- quantum Monte Carlo;
- Holonomic constraints;
- Ramachandra space;
- diffusion Monte Carlo;
- path integral Monte Carlo
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.