Loading Initial Structures

Last updated: October 16, 2026

Prepared structures can be used as the initial structures for a search. Setting load_struc_flag = True in the [option] section of cryspy.in loads ./data/pkl_data/init_struc_data.pkl on the first run. The default is False. If fewer structures are loaded than required, the remaining structures are generated randomly.

Usage

[option]
load_struc_flag = True

See Tutorial > Loading Initial Structures for an example that converts three CIF files and loads the resulting data. CrySPY Utility’s pos2pkl.py can convert structure files to init_struc_data.pkl.

Checks During Loading

The following conditions are checked when loading. If a condition is not satisfied, an error is raised and initialization stops.

The data in init_struc_data.pkl must be a dictionary.
Structure IDs must be consecutive integers starting from 0: for example, 0, 1, and 2 for three structures.
Each structure must be a pymatgen Structure object.
The number of structures must not exceed the limit below.

Algorithm	Maximum number of structures
EA, EA-vc	`n_pop`
RS, BO, LAQA	`tot_struc`

See Data Format > Initial and Optimized Structure Data for format details.

Atom Types, Atom Counts, and Composition Checks

In RS, BO, LAQA, and EA, the atom types and the number of atoms of each type must match atype and nat. Structures with different atom counts cannot be used, even if their composition ratios are the same.

In EA-vc, the following conditions are checked.

Item	Condition
Atom types	Only atom types listed in `atype` are present.
Atom counts	Each atom count is within the bounds specified by `ll_nat` and `ul_nat`, and the structure contains at least one atom in total.
Composition constraints	Any composition range specified by `min_comp` or `max_comp` is satisfied.
Charge neutrality	If `charge` is specified, neutrality can be achieved with a combination of the specified oxidation states.

See Composition Constraints and Charge Neutrality Condition for details. The loading checks do not enforce mindist, space-group constraints, or cell-volume constraints.

Filling Missing Structures

If fewer structures are loaded than tot_struc or n_pop, the remaining structures are generated randomly. Additional structures receive consecutive IDs following the last loaded ID. The loaded and additional structures are saved together to ./data/pkl_data/init_struc_data.pkl and ./data/init_POSCARS.