Butadiene Diffusion Monte Carlo¶

This tutorial covers a Diffusion Monte Carlo (DMC) calculation on Butadiene (\(C_4H_6\)) using BFD pseudopotentials and a large determinant expansion (500 determinants).

System Configuration¶

Molecule: Butadiene (\(C_4H_6\))
Pseudopotential: BFD (Burkatzki-Filippi-Dolg)
Basis Set: BFD-T (Triple-zeta quality)
Wavefunction: 500 Determinants (from CIPSI)
Method: DMC

Input File Setup¶

Input File: dmc.inp

%module general
    title        'butadiene'
    pool         'pool/'
    pseudopot    BFD
    basis        BFD-T
    mode         'dmc_one_mpi1'
%endmodule

# Load molecular geometry
load molecule        $pool/champ_v3_butadiene.xyz

# Load basis set info
load basis_num_info  $pool/champ_v3_BFD-T_basis_pointers.bfinfo

# Load wavefunction components
load determinants    TZ_1M_500.det
load orbitals        champ_v3_trexio_order_ci1010_pVTZ_1_orbitals.lcao
load jastrow         jastrow_good_b3lyp.0
load jastrow_der     jastrow.der
load symmetry        ci1010_pVTZ_1_symmetry.sym

%module electrons
    nup           11
    nelec         22    # 22 valence electrons (C:4*4 + H:6*1)
%endmodule

%module blocking_dmc
    dmc_nstep     60    # Steps per block
    dmc_nblk      10    # Number of blocks
    dmc_nblkeq    1     # Equilibration blocks
    dmc_nconf     20    # Target population per walker file
%endmodule

%module dmc
    tau           0.05      # Component time step
    etrial        -26.3d0   # Trial energy guess (Hartree)
    icasula       -1        # Standard DMC algorithm
%endmodule

Running the Calculation¶

This calculation uses dmc_one_mpi1 mode, suitable for MPI parallelization. It requires pre-optimized Jastrow factors (jastrow_good_b3lyp.0) and a determinant file (TZ_1M_500.det).

Resources for this test can be found in the Butadiene CI Test folder.