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VMC Optimization

(Reference: tests/CI_test/VMC-TREXIO-H2O-DFT-optall)

This workflow describes how to optimize all parameters of the wavefunction (Jastrow, Orbitals, CI coefficients) using VMC.

Steps

  1. Input Preparation:

    • Load the TREXIO file containing the starting orbitals (e.g., from DFT).
    • Define the Jastrow factor (or load a starting one).

  2. Input Configuration:

    • Set ioptwf = 1 to enable optimization.
    • Set ioptjas = 1, ioptorb = 1, ioptci = 1 to optimize all sets of parameters.
    • Choose an optimization method (e.g., method = 'sr_n' for Stochastic Reconfiguration or method = 'linear' for the Linear Method).

  3. Execution:

    • Run CHAMP.
    • Monitor the energy and gradient norm in the output.

Example Input

%module optwf
    ioptwf        1
    ioptjas       1
    ioptorb       1
    ioptci        0  # Set to 1 if using multi-determinant WF
    method        'sr_n'
    nopt_iter     20
    sr_tau        0.05
%endmodule

Tips

  • Start by optimizing Jastrow only (ioptjas=1, ioptorb=0).
  • Then optimize Jastrow + Orbitals together.
  • Use vmc_nblk_max to increase the precision as the optimization proceeds.