DFT Calculator

We have implemented both VASP and CP2K for first principle calculaton. In future we planned to additional calculators. Most of the settings inside dft_calculator section are default and will work as it is. However for both the calculators an additional input file is required which native to the calculator user has chosen. This might seems redundant however, it provides more fexibilty to the users of choosing their own template for any system of choice.

For VASP user can parse thier own INCAR file with all the input keywords native to VASP. See more in ASE VASP documentaition

Class : SetupDFTCalculator

VASP

# DFT calculator settings
dft_calculator:
  name: "VASP"               # DFT package name
  prec: "Normal"             # Precision level
  kgamma: True               # Gamma point calculation
  incar_file: "INCAR"        # Path to INCAR file
  exe_command: "/path/to/VASP/bin/vasp_std"  # Full command to run VASP with MPI

A minimal INCAR is given below,

# Global Parameters #
SYSTEM = AmmoniaBorate
ISTART = 0
ICHARG = 2
ISPIN  = 1
ENCUT  = 300
LCHARG = .FALSE.
LWAVE  = .FALSE.
# Electronic Relaxation #
ISMEAR = 0
SIGMA  = 0.05
EDIFF  = 1E-05

CP2K

# CP2K calculator
dft_calculator:
    name: "CP2K" # DFT package name
    template_file: "cp2k_template.inp" # Path to INCAR file
    exe_command: "mpirun -np 2 /path/to/cp2k/exe/local/cp2k_shell.psmp"

A minimal CP2K input template file (cp2k_template.inp) is given below,

! This is a comment
# This is a comment
&GLOBAL
ECHO_INPUT
&END GLOBAL
&FORCE_EVAL
&DFT
    CHARGE 0
    MULTIPLICITY 1
&MGRID
    REL_CUTOFF 25
    NGRIDS 3
&END MGRID
&QS
    METHOD GPW #GAPW
    EPS_DEFAULT 1.0E-12
    EPS_PGF_ORB 1.0E-14
    EXTRAPOLATION ASPC
    EXTRAPOLATION_ORDER 3
&END QS

&SCF
  EPS_SCF 1.0E-4
  &OT
    PRECONDITIONER FULL_ALL
  &END
  &OUTER_SCF
    EPS_SCF 1.0E-4
    MAX_SCF 3
  &END
  SCF_GUESS RESTART
&END SCF
&END DFT

&SUBSYS
    &KIND B
      ELEMENT O
    &END KIND
    &KIND H
      ELEMENT H
    &END KIND
    &KIND N
      ELEMENT N
    &END KIND
&END SUBSYS
&END FORCE_EVAL

Note

Ensure that the executable path is correctly specified in exe_command key inside the yaml file.

Example Use

import os
from ase import Atoms
from ase.io import read, write
from sparc.src.calculator import dft_calculator

# VASP input file
incar = """
# Global Parameters #
SYSTEM = Water
ISTART = 0
ICHARG = 2
ISPIN  = 1
ENCUT  = 300
LCHARG = .FALSE.
LWAVE  = .FALSE.
# Electronic Relaxation #
ISMEAR = 0
SIGMA  = 0.05
EDIFF  = 1E-05
"""
# save file in INCAR format
with open("INCAR", 'w') as file:
    file.write(incar)

# required configuration setup
config = {
    "dft_calculator": {
        "name": "VASP",
        "prec": "Normal",
        "kgamma": True,
        "incar_file": "INCAR",
        "exe_command": "/path/to/VASP/bin/vasp_std",
    }
}

# Structure
atoms = Atoms('H2O')
atoms.set_cell([8.0, 8.0, 8.0])
atoms.set_pbc([True, True, True])
print (atoms)

# Build calculator and attach to atoms object
calc = dft_calculator(config, print_screen=True)
atoms.calc = calc
print("VASP energy (eV):", atoms.get_potential_energy())

output:

Atoms(symbols='H2O', pbc=True, cell=[8.0, 8.0, 8.0])
[SPARC][INFO] ==================================================
[SPARC][INFO]               INCAR PARAMETERS
[SPARC][INFO] ==================================================
[SPARC][INFO]   SYSTEM : Water
[SPARC][INFO]   ISTART : 0
[SPARC][INFO]   ICHARG : 2
[SPARC][INFO]   ISPIN  : 1
[SPARC][INFO]   ENCUT  : 300.0
[SPARC][INFO]   LCHARG : False
[SPARC][INFO]   LWAVE  : False
[SPARC][INFO]   ISMEAR : 0
[SPARC][INFO]   SIGMA  : 0.05
[SPARC][INFO]   EDIFF  : 1e-05
[SPARC][INFO] ==================================================

VASP energy (eV): -400.43427628

API Reference

class sparc.src.calculator.SetupDFTCalculator(input_config, print_screen=False)[source]

Bases: object

Module to set up DFT calculators using ASE atom objects.

Parameters:

input_config (dict) – Dictionary containing configuration for the DFT calculator.
print_screen (bool, optional) – Prints input parameters on the output file. [default: False]

cp2k()[source]

Set up the CP2K calculator.

Returns:: The configured CP2K calculator object, or None if an error occurs.
Return type:: CP2K or None

vasp()[source]

Set up the VASP calculator.

Returns:: The configured VASP calculator object, or None if an error occurs.
Return type:: VASP or None

sparc.src.calculator.dft_calculator(config, print_screen=False)[source]

Helper function to set up the DFT calculator based on configuration.

Parameters:

config (dict) – Dictionary containing the full DFT configuration.
print_screen (bool, optional) – Whether to print the calculator details to the screen.

Returns:

The configured ASE calculator instance.

Return type:

ASE Calculator