QMC runs : Check that the setup is OK

First, we can compute with QP the energies of the single-determinant wave functions with the 2 different sets of MOs.

qp set_file h2o_hf
qp run print_energy

qp set_file h2o_dft
qp run print_energy

These commands return the energy of the wavefunction contained in the EZFIO database. These values will be useful for checking that the QMC setup is OK. You should obtain the energies:

We will now convert the TREXIO files into input files suitable for CHAMP:

You need the resultsFile and trexio Python packages. They can be installed with pip as described in .

Create a new directory named H2O_HF and copy the TREXIO file h2o_hf.trexio into it. Go inside this directory and run

python3 ~filippi/Tutorial-QMC-School/trex2champ.py --trex "h2o_hf.trexio" \
                       --motype  "Canonical" \
                       --backend "HDF5" \
                       --basis_prefix "BFD-cc-pVDZ" \
                       --lcao \
                       --geom \
                       --basis \
                       --ecp \
                       --det

Many files were created. Now, create a directory named pool, and move some files into the pool:

mkdir pool
mv *.xyz *bfinfo BFD-* ECP* pool

You can now create an input file for CHAMP vmc_h2o_hf.inp :

%module general
    title           'H2O HF calculation'
    pool            './pool/'
    pseudopot       ECP
    basis           BFD-cc-pVDZ
    mode            'vmc_one_mpi1'
%endmodule


load molecule        $pool/champ_v2_h2o_hf_geom.xyz
load basis_num_info  $pool/champ_v2_h2o_hf_with_g.bfinfo

load orbitals        champ_v2_h2o_hf_orbitals.lcao
load determinants    champ_v2_h2o_hf_determinants.det
load jastrow         jastrow.start

%module electrons
    nup           4
    nelec         8
%endmodule


%module blocking_vmc
    vmc_nstep     20
    vmc_nblk      20000
    vmc_nblkeq    1
    vmc_nconf_new 0
%endmodule

Create the file for the Jastrow factor as follows, and save it as jastrow.start:

jastrow_parameter   1
  0  0  0           norda,nordb,nordc
   0.60000000   0.00000000     scalek,a21
   0.00000000   0.00000000   (a(iparmj),iparmj=1,nparma)
   0.00000000   0.00000000   (a(iparmj),iparmj=1,nparma)
   0.00000000   1.00000000   (b(iparmj),iparmj=1,nparmb)
 (c(iparmj),iparmj=1,nparmc)
 (c(iparmj),iparmj=1,nparmc)
end

This files implies that there is no Jastrow factor \(\exp(J)=1\).

Create the submission script as presented in , and submit the job. You should obtain the Hartree-Fock energy.

Now reproduce the same steps for the TREXIO file containing the DFT orbitals in directory H2O_DFT.

The energies obtained with VMC without the Jastrow factor should be the same as those computed by QP at the beginning of this section.