General Keywords and Load Commands¶

This section describes the common keywords used in the %module general block and the various load commands used to define the system and wavefunction components.

The `general` module¶

The general module sets up the fundamental parameters for the calculation.

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

Basic Setup¶

Title

Defines a descriptive title for the run, which is printed to the output.
```
title 'Butadiene Optimization'
```

Pool

Sets the default directory prefix for file paths accessed via the $pool variable.
```
pool './pool/'
```

Mode

Specifies the type of calculation to run.
```
mode 'vmc_one_mpi'
```
View Calculations

System Configuration¶

Pseudopotential

Specifies the type of pseudopotential being used.
```
pseudopot 'BFD'
```
Effective Core Potentials

Basis

Specifies the basis set type.
```
basis 'BFD'
```
Basis Sets

nloc

Number of localized electrons (pseudo-electrons). Set to 0 for all-electron or standard ECP.
```
nloc 0
```

State-Specific / Multi-State Options¶

nstates

Number of electronic states involved in the calculation.
```
nstates 2
```

weights

Array of weights for each state in the optimization target function.
```
weights [ 0.5, 0.5 ]
```

weights_guiding

Array of weights defining the guiding wavefunction $\Psi_G$.
```
weights_guiding [ 1.0, 0.0 ]
```

sr_lambda

Array of state-specific shift (?) parameters for importance sampling.
```
sr_lambda [ 1.0d0 ]
```

anorm

Array of normalization constants for each state.
```
anorm [ 1.0, 0.32 ]
```

File Loading Commands¶

CHAMP uses load commands to import data from external files. These commands are placed outside of %module blocks.

System Geometry & Basis¶

Molecule

Reads atomic coordinates (typically in CHAMP-XYZ format).
```
load molecule butadiene.xyz
```
Molecular Geometry

Basis Info

Reads basis set definitions and pointer information.
```
load basis_num_info BFD-T.bfinfo
```
Basis Set Pointers

Lattice

Reads lattice vectors for periodic systems. This can be done by loading an external file or determining periodic cell parameters in a block in the input file.

Option 1: External File
```
load lattice box.txt
```
Option 2: Input Block You can specify the lattice parameters directly in the input file using a %block lattice structure. This supports both cubic (single value) and general (3 vectors) cells, with optional unit specifications.

Cubic Cell Example:
```
%block lattice
  10.26
%endblock
```
```
%block lattice
  10.26  Bohr
%endblock
```
General Cell Example:
```
%block lattice
  10.0   0.0   0.0  Ang
   0.0  10.0   0.0  Ang
   0.0   0.0  10.0  Ang
%endblock
```
Supported units include Bohr (default), Ang (Angstrom), m, nm, etc.

Wavefunction Components¶

Determinants

Reads the determinant expansion (CI) and CSF definitions.
```
load determinants ci.det
```
Determinants

Orbitals

Reads molecular orbital coefficients.
```
load orbitals orbitals.lcao
```
Molecular Orbitals

Jastrow

Reads Jastrow factor parameters.
```
load jastrow jastrow.Start
```
Jastrow Factors

Jastrow Deriv.

Reads Jastrow derivative mappings.
```
load jastrow_der jastrow.der
```

Symmetry

Reads symmetry information for the system.
```
load symmetry molecule.sym
```

TREXIO and QMCkl¶

TREXIO

Loads geometry, basis, orbitals, and determinants from a single TREXIO file.
```
load trexio molecule.hdf5
```
TREXIO Guide