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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Molecular Structure

CPP 33.7: Vortrag

Donnerstag, 28. Februar 2008, 16:30–16:45, C 230

Exact and approximate forces in the diffusion Monte Carlo method — •A. Badinski and R. J. Needs — Theory of Condensed Matter Group, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, United Kingdom

The problem of calculating accurate inter-atomic forces within the diffusion Monte Carlo (DMC) method has been a long-standing issue[1-3]. The DMC method is highly successful for calculating ground-state total energies of many-electron systems, but there is still a lack of an accurate and efficient way of calculating forces. Therefore, DMC calculations are usually performed using geometries obtained from either density-functional theory or conventional quantum chemistry methods, or from experiment. In this talk, we present exact expressions for DMC forces and give a practical scheme of estimating them[4]. Equilibrium geometries are derived from DMC forces and compared with those obtained from DMC potential energy curves. Results for four small molecules show that the equilibrium bond lengths obtained from the force and energy calculations are in very good agreement.

[1] C. Filippi, C. J. Umrigar, Phys. Rev. B 61, 16291 (2000)

[2] R. Assaraf, M. Caffarel, J. Chem. Phys. 119, 10536 (2003)

[3] A. Badinski, R. J. Needs, Phys. Rev. E 76, 036707 (2007)

[4] A. Badinski, R. J. Needs, Phys. Rev. B (accepted for publication)