3.3 Specific/ folder

Executables and enumerated input files for structure relaxation should be put in subdirectory /StructurePrediction/Specific/ for different interfaced code, such as VASP, SIESTA, GULP, etc..

• For VASP, files INCAR_1, INCAR_2, …, etc., defining how relaxation and energy calculations will be performed at each stage of relaxation (we recommend at least 3 stages of relaxation), and the corresponding POTCAR_* files with pseudopotentials. E.g., INCAR_1 and INCAR_2 perform very crude structure relaxation of both atomic positions and cell parameters, keeping the volume fixed, INCAR_3 performs full structure relaxation under constant external pressure with medium precision, INCAR_4 performs very accurate calculations. Each higher-level structure relaxation starts from the results of a lower-level optimization and improves them. POTCAR files can alternatively be defined by just putting the files for the elements in Specific/ folder, for instance POTCAR_C, POTCAR_O, etc.

• For SIESTA, you need the pseudopotentials files and input files input_1.fdf,
  input_2.fdf, …

• For GULP, files goptions_1, goptions_2, …, and ginput_1, ginput_2, …must be present. The former specify what kind of optimization is performed, the latter specify the details (interatomic potentials, pressure, temperature, number of optimization cycles, etc.).

• For DMACRYS, fort.22 is the file for general control parameters. The classical force field is given by the file of fit.pots. File cutoff defines the maximum bond length of the intra-molecular bonds.

• For CASTEP, structural files are given by cell_1, cell_2, …, while the computational parameters are given by param_1, param_2, …. The corresponding pseudopotential files must be present as well.

• For CP2K, files cp2k_options_1, cp2k_options_2, …, must be present. All files should be normal CP2K input files with all parameters except atom coordinates and cell parameters (these will be written by USPEX together with the finishing line “&END FORCE_EVAL”). The “name of the project” should always be USPEX, since the program reads the output from files USPEX-1.cell and USPEX-pos-1.xyz. We recommend performing relaxation at least in three steps (similarly to VASP) — first optimize only the atom positions with the lattice fixed, and then do a full relaxation.

• For Quantum Espresso, files qEspresso_options_1, qEspresso_options_2, …, must be present. All files should be the normal QE input files with all parameters except atom coordinates, cell parameters and -points (these will be written by USPEX at the end of the file). We recommend performing a multi-step relaxation. For instance, qEspresso_options_1 does a crude structure relaxation of atomic positions with fixed cell parameters, qEspresso_options_2 does full structure relaxation under constant external pressure with medium precision; and qEspresso_options_3 does very accurate calculations.