Butadiene Geometry Optimization¶

This tutorial demonstrates a VMC calculation with a large determinant expansion (64,000 determinants) that includes geometry force analysis settings, preparing for geometry optimization.

System Configuration¶

• Molecule: Butadiene
• Expansion: ~64,000 Determinants (RAS1022 SDT)
• Basis: BFD-Q

Input File Setup¶

Input File: vmc_opt_ras1022_pVQZ_65000.inp

%module general
    title        'butadiene vmc optimization 65000 dets'
    mode         vmc_one_mpi
%endmodule

load determinants    ras1022_SDT_pVQZ_determinants_state1.det
# ... load orbitals, jastrow ...

%module optwf
    ioptwf        1
    ioptci        1
    ioptjas       1
    ioptorb       1
    method        'sr_n'
    nextorb       500
%endmodule

%module optgeo
    iforce_analy  1      # Enable force analysis
    iuse_zmat     0      # Use Cartesian coordinates
    alfgeo        0.25d0 # Step size factor for geometry update
%endmodule

Description¶

The optgeo module controls geometry optimization parameters. iforce_analy 1 computes atomic forces. alfgeo sets the scaling for the geometry update step if optimization were fully enabled (though often this is done via external drivers or specific modes).

Resources: Butadiene Geo Opt Test