Quantum chemistry by quantum Monte Carlo: beyond ground-state energy calculations
We present recent advances with the quantum Monte Carlo (QMC) method in its application to molecular systems. The QMC method is a procedure for solving the Schroedinger equation statistically, by the simulation of an appropriate random process. The formal similarity of the Schroedinger equation with a diffusion equation allows one to calculate quantum mechanical expectation values as Monte Carlo averages over an ensemble of random walks. We have previously obtained highly accurate correlation energies for a number of molecules, as well as the singlet-triplet splitting in methylene and the barrier height for the H + H/sub 2/ exchange reaction. Recently we have begun a program of extending the QMC approach to the calculation of analytic derivatives of the energy. A brief description of the approach is presented here, together with some preliminary results. In addition, we are now computing expectation values of properties other than the energy. We summarize how standard QMC must be modified, and present some results for H/sub 2/ and N/sub 2/. Finally, we describe preliminary work toward the goal of obtaining accurate molecular excited states through QMC. 24 refs., 5 tabs.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6333811
- Report Number(s):
- LBL-20089; CONF-850859-2; ON: DE86003993
- Resource Relation:
- Conference: 5. international congress on quantum chemistry, Montreal, Canada, 19 Aug 1985; Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
CHEMICAL REACTION KINETICS
QUANTUM MECHANICS
MONTE CARLO METHOD
CONFIGURATION INTERACTION
DIFFUSION
EXCITED STATES
MOLECULES
SCHROEDINGER EQUATION
SELF-CONSISTENT FIELD
DIFFERENTIAL EQUATIONS
ENERGY LEVELS
EQUATIONS
KINETICS
MECHANICS
PARTIAL DIFFERENTIAL EQUATIONS
REACTION KINETICS
WAVE EQUATIONS
657002* - Theoretical & Mathematical Physics- Classical & Quantum Mechanics