Skip to content

Wavefunction Optimization

Wavefunction optimization is a critical step in QMC calculations. It involves adjusting the parameters of the trial wavefunction (Jastrow factors, orbital coefficients, CI coefficients) to minimize the energy or variance.

Overview

CHAMP supports several optimization algorithms, controlled by the optwf module.

Key Concepts

  • Parameters: The variables being optimized (e.g., Jastrow coefficients, orbital rotation parameters).
  • Cost Function: The quantity being minimized (usually energy, variance, or a combination).
  • Algorithm: The numerical method used to update parameters (e.g., Stochastic Reconfiguration, Linear Method).

Input Keywords

The optwf module controls the optimization process.

%module optwf
    ioptwf        1       # Enable optimization
    ioptjas       1       # Optimize Jastrow parameters
    ioptorb       0       # Optimize orbitals (0=no, 1=yes)
    ioptci        0       # Optimize CI coefficients

    method        'sr_n'  # Optimization method (sr_n, lin_d, linear)
    nopt_iter     20      # Number of optimization iterations
    nblk_max      4000    # Max blocks per iteration

    sr_tau        0.05    # Step size for SR
    sr_eps        0.001   # Regularization for SR
%endmodule

Available Methods

  • Energy Minimization: Minimizing the energy using Stochastic Reconfiguration (SR) or other gradient-based methods.
  • Linear Method: A robust method that can minimize energy, variance, or a mix.
  • Variance Minimization: Minimizing the variance of the local energy (often used for initial optimization).