Roi Baer
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The Chaim Weizmann Institute of Chemistry, and the Fritz Haber Research Center for Molecular Dynamics,
The Hebrew University of Jerusalem, Jerusalem 91904, Israel. Tel: +972-2-658-6114 Fax: +972-2-651-3742
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QMC

למעלה
Plane waves
Splitting
Review
Well-tempered

Shifted Contour Auxiliary-Field Monte-Carlo

We developed a new QMC method (see bellow) called Shifted Contour Auxiliary-Field Monte Carlo for electronic structure.

See our work on QMC:

bulletStraddling the sign problem using SCAFMC
bulletElectronic structure using SCAFMC, Plane waves and pseudopotentials
bulletMolecular spectroscopic constants using correlated sampling SCAFMC with  application to N2.
bulletMolecular deformation barriers with application to the barrier to linearity of H2O. 
bulletSingle triplet splitting
bulletReview of AFMC
bulletWell Tempered AFMC: Gaussian based AFMC (connects to GAMESS), error sources and convergence tunings.
Quantum Monte Carlo (QMC)

QMC methods offer a non- perturbative means for systematically improving the quality of electronic structure calculations, scaling gently with number of electrons.

The established Quantum Monte-Carlo methods for calculating ground state properties of chemical and materials science systems are:

  1. Variational (VMC)
  2. Diffusion and Greens Function (DMC/GFMC)
  3. Path integral (PIMC)

 

 The Sign Problem

Pauli Principle (PP): Electronic wave function must be antisymmetric to exchange of coordinates of two electrons. In different QMC methods PP manifests itself in different ways. Always making trouble for us! This is called "Fermion Sign Problem".

How each method handles the problem:

  1. VMC: antisymmetric trial function
  2. DMC/GFMC: Fixed nodes from HF determinant.
  3. PIMC restricted paths

Causes uncontrolled approximations.