Quantum Monte Carlo for molecules
An alternative approach to conventional quantum chemistry techniques for molecular studies is described. This approach uses the quantum Monte Carlo method, which was developed and used primarily in nuclear and condensed-matter physics. In this approach the many-body Schroedinger equation is re-interpreted as a diffusion equation. Simulation of the appropriate random walk process allows one to calculate expectation values of molecular properties. In principle these expectation values can be calculated exactly, subject only to statistical errors (which may be made arbitrarily small). In preliminary work on small molecules (H/sub 2/, LiH, Li/sub 2/, and H/sub 2/O), we use a simple but accurate approximation to ease the treatment of Fermi statistics. In that approximation, the calculated total energy remains an upper bound to the true energy. How good the bound is, as well as the magnitude of the statistical error, depends on the quality of an importance function which guides the diffusion into more probable regions of phase space. With relatively simple importance functions, we obtain from 75 to 100% of the correlation energy of the above-mentioned molecules.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5343552
- Report Number(s):
- LBL-16753; CONF-830589-3; ON: DE84005171
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
Molecular & Chemical Physics-- Atomic & Molecular Properties & Theory
74 ATOMIC AND MOLECULAR PHYSICS
ALKALI METAL COMPOUNDS
ALKALI METALS
CORRELATIONS
ELECTRON CORRELATION
ELEMENTS
ENERGY LEVELS
GROUND STATES
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
LITHIUM
LITHIUM COMPOUNDS
LITHIUM HYDRIDES
MECHANICS
METALS
MOLECULES
MONTE CARLO METHOD
NONMETALS
OXYGEN COMPOUNDS
QUANTUM MECHANICS
WATER