5.1. [sampling] section

Specify the parameters of the replica exchange Monte Carlo part, such as the number of replicas, the temperature range, and the number of Monte Carlo steps. The example is shown as follows.

[sampling]
nreplicas = 3
nprocs_per_replica = 1
kTstart = 500.0
kTend = 1500.0
nsteps = 5
RXtrial_frequency = 2
sample_frequency = 1
print_frequency = 1

5.1.1. Input Format

Specify a keyword and its value in the form keyword = value. Comments can also be entered by adding # (Subsequent characters are ignored).

5.1.2. Keywords

  • About temperatures

    • kTstart

      Format : float (>0)

      Description : Minimum temperature for the replica.

    • kTend

      Format : float (>0)

      Description : Maximum temperature for the replica.

  • About replica

    • nprocs_per_replica

      Format : int (natural number)

      Description : The number of processes for the replica. Default value = 1.

    • nreplicas

      Format : int (natural number)

      Description : The number of replicas.

  • Others

    • nsteps

      Format : int (natural number)

      Description : Number of Monte Carlo steps.

    • RXtrial_frequency

      Format : int (natural number)

      Description : The interval for performing replica exchange trials. For example, setting this value to 1 means that replica exchange is attempted at every Monte Carlo step, while setting this to 2 means that exchange is attempted at every second step. Default = 1.

    • sample_frequency

      Format : int (natural number)

      Description : The interval for observation of physical quantities. Default value = 1.

    • print_frequency

      Format : int (natural number)

      Description : The interval for saving physical quantities. Default value = 1.

    • reload

      Format : bool (“true” or “false”)

      Description : Whether to restart a prior calculation from the last step finished last time. Default value = false.

5.2. [sampling.solver] section

This section specifies solver parameters such as solver type (VASP, QE, …), path to solver, directory with solver-specific input file(s). An example is shown as follows:

[sampling.solver]
type = 'vasp'
path = './vasp'
base_input_dir = './baseinput'
perturb = 0.1
run_scheme = 'mpi_spawn_ready'

5.2.1. Input Format

Keywords and their values are specified by a keyword and its value in the form keyword = value. Comments can also be entered by adding # (Subsequent characters are ignored).

5.2.2. Keywords

  • type

    Format : str

    Description : The solver type (OpenMX, QE, VASP, aenet).

  • path

    Format : str

    Description : The path to the solver.

  • base_input_dir

    Format : str or list of str

    Description : The path to the base input file. If multiple calculations are set up in the form of a list, each calculation using each input is performed in turn. For the second and subsequent calculations, the structure from the last step of the previous calculation is used as the initial coordinates, and the energy from the last calculation is used. For example, it is possible to perform a fast structural optimization in the first input file at the expense of accuracy, and then perform the structural optimization in the second and later input files with a higher accuracy setting. Or, in the case of grid vector relaxation, one can run the same input multiple times to reset the computational mesh based on a set plane-wave cutoff.

  • perturb

    Format : float

    Description : If a structure with good symmetry is input, structure optimization tends to stop at the saddle point. In order to avoid this, an initial structure is formed by randomly displacing each atom in proportion to this parameter. It can also be set to 0.0 or false. Default value = 0.0.

  • ignore_species

    Format : list

    Description : Specify atomic species to “ignore” in neural network models such as aenet. For those that always have an occupancy of 1, it is computationally more efficient to ignore their presence when training and evaluating neural network models.

  • run_scheme

    Format : str

    Description : Way to invoke the solver program. For details, please see Specific notes for first-principles solvers

  • parallel_level (Only for QuantumESPRESSO)

    Format : dict

    Description : How to split parallel cpu resources, i.e., Parallelization levels . Key names are long-form command-line options (without the leading hyphen), that is, nimage, npools, nband, ntg, and ndiag. Values are the number of parallelization. Only the specified elements will be passed to pw.x as command-line options.