Brock University - Department of Chemistry

Accurate Computed Physical Properties Other than the Energy.

Naturally there is a strong interest in energy-related physical properties, such as the force constant and other spectroscopic constants. For example, Belohorec et al (1993) applied Monte Carlo methods to estimate these for the first time for a transition metal containing molecule: CuH.

It is a challenge to estimate physical properties other than the energy, because the electron distribution obtained in quantum Monte Carlo (QMC) is not sufficiently accurate for these properties. In principle, the exact electron distribution is required, the square of the exact wavefunction.

Although we do not have an analytic form for the exact wavefunction, we know how to sample it by Monte Carlo methods. Recently Langfelder et al (1997) have developed a quantum Monte Carlo (QMC) algorithm, practical for small system simulations, where indeed we can sample from the "exact" electron distribution.

Previously Vrbik et al (1990) designed Monte Carlo methodologies to estimate physical properties other than the energy (polarizability, hyperpolarizability, shielding factors, etc.); these apply in the exact sampling regime, promising higher accuracy for these properties.

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