Quantum chemistry by quantum Monte Carlo: beyond ground-state energy calculations

Conference · Thu Aug 01 04:00:00 EDT 1985

OSTI ID:6333811

Reynolds, P J; Barnett, R N; Hammond, B L; Grimes, R; Lester, Jr, W A

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
• Country of Publication: United States
• Language: English

Related Subjects

657002* -- Theoretical & Mathematical Physics-- Classical & Quantum Mechanics
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
CHEMICAL REACTION KINETICS
CONFIGURATION INTERACTION
DIFFERENTIAL EQUATIONS
DIFFUSION
ENERGY LEVELS
EQUATIONS
EXCITED STATES
KINETICS
MECHANICS
MOLECULES
MONTE CARLO METHOD
PARTIAL DIFFERENTIAL EQUATIONS
QUANTUM MECHANICS
REACTION KINETICS
SCHROEDINGER EQUATION
SELF-CONSISTENT FIELD
WAVE EQUATIONS