VASP Execution Tutorial

Applies to: rmc_dft v0.6.13

This tutorial describes running VASP independently by executing rmc_vasp.py directly, as well as using rmc_vasp_init.py.

1. Overview

rmc_vasp.py runs VASP using existing VASP input files.

VASP input conditions are specified in rmc_vasp_init.py.

config.yml
    |
rmc_vasp_init.py
    |
    +--> KPOINTS
    +--> POTCAR
    +--> VaspIncar.init()
    +--> Set INCAR tags
    |
rmc_vasp.py
    |
    +--> run_vasp()
            |
            +--> Execute VASP
            +--> postprocess
            +--> Save to logN_dft

2. Required Files

A typical setup includes:

config.yml
rmc_vasp.py
rmc_vasp_init.py
POSCAR

INCAR, KPOINTS, and POTCAR can either be provided as existing files or prepared by the initialization script.

3. `rmc_vasp_init.py`

When rmc_vasp.py is launched directly, the following function is called before VASP execution:

run_vasp_init(
    config=config_,
    vasp_incar=vasp_incar_,
    logger=logger_,
)

KPOINTS

The current initialization script creates KPOINTS only if it does not already exist:

if not os.path.exists("KPOINTS"):
    ...

An existing KPOINTS file is used unchanged.

POTCAR

Likewise, POTCAR is created only when it is absent.

Element information is taken from config.element_info.

INCAR

For INCAR, first execute:

vasp_incar.init()

This initialization corresponds to rmc_dat.init() on the RMC side.

4. `VaspIncar.init()`

In v0.6.13, VASP also has an explicit initialization procedure.

Its basic behavior is:

INCAR exists
    -> Read the existing INCAR
    -> init() itself does not rewrite it

INCAR does not exist
    -> Create an initial INCAR

Already initialized
    -> init() does not initialize again

After initialization, explicitly configured tags are set in rmc_vasp_init.py, for example:

vasp_incar.set_tag("EDIFF", 1e-4)
vasp_incar.set_tag("EDIFFG", 1e-3)
vasp_incar.set_tag("ISMEAR", 0)
vasp_incar.set_tag("SIGMA", 0.1)
vasp_incar.set_tag("NSW", 30)
vasp_incar.set_tag("ISIF", 2)
vasp_incar.set_tag("IBRION", 2)

Importantly, the initialization script is not skipped when an existing INCAR is present.

The existing INCAR is loaded as the initial input, and the setters in rmc_vasp_init.py are then applied.

5. Execution

Run:

python rmc_vasp.py

The execution mode normally comes from run_mode in config.yml.

Inside run_vasp(), VASP is launched using:

if run_mode is None:
    run_mode = config.run_mode

6. Postprocessing

After VASP finishes, postprocessing is normally performed:

vasp.postprocess(
    log_dir=log_dir_vasp,
    cfg_name=config.cfg_name,
)

This archives calculation results and converts or updates the structural files required by the next RMC calculation.

7. Log Directories

The destination is determined by:

next_log_dir_name("dft")

For example:

log0_dft
log1_dft
log2_dft
...

In RMC-DFT operation, the numeric part is a shared sequence number across RMC and DFT.

8. `CONTINUE_NUMBERED_INIT`

rmc_vasp_init.py contains:

CONTINUE_NUMBERED_INIT = False

This is normally unused when rmc_vasp.py is run independently.

When invoked through rmc_vasp_script.py / rmc_vasp_script_sequence.py with a numbered initialization file:

rmc_vasp_init_N.py

it determines whether the numbered initialization file continues to be used for subsequent VASP runs.

9. General Editing Guidelines

To change VASP conditions, edit rmc_vasp_init.py rather than the main rmc_vasp.py script.