4. Preparation of initial structures for DFT calculations

4.1. mkposcar

  • This program searches for symmetric operations and generates independent DFT structures.

  • Generating high symmetric structures or random structures.

  • Crystal lattice is determined by UPOSCAR and UPOTCAR files.

  • Available only for binary systems.

  • Available for multi-thread calculations using OPENMP.

Input files

Output files

  • POSCAR_1 - POSCAR_nstruct

4.2. MKPOS.in

Example

Generating 5 structures with a lattice constructed by the 2x2x1 expansion of a 4-atoms unit cell (16-atoms cell). The structures have 12 A-atoms and 4 B-atoms.

ISUB = 1
NUCELL = 2 2 1
NCHANGE = 4
NSTRUCT = 5
SELECT = Highsym

4.2.1. ISUB tag

Sublattice indexes for considering atomic configurations. Atomic configurations are considered on ISUBth lattice sites of UPOSCAR (line 6).

  • Default : 1

  • Example : ISUB = 1 3

4.2.2. NUCELL tag

Independent atomic configurations are searched for on the lattice constructed by the NUCELL expansion of the unit cell.

  • Default : none

  • Example : NUCELL = 2 2 2

4.2.3. NCHANGE tag

Number of atoms. In N-nary systems, set N-1 kinds of atoms. The number of the other kind of atoms is automatically set to (number of lattice sites - NCHANGE).

  • Default : none

  • Example : NCHANGE = 6 2

4.2.4. NSTRUCT tag

Number of structures.

  • Default : none

  • Example : NSTRUCT = 10

4.2.5. SELECT tag

SELECT tag detemines how to generate structures.

  • Default : Highsym

  • SELECT = Highsym : generating high symmetric structures

  • SELECT = Random : generating random structures

4.2.6. IOUT tag

  • Default : 1

  • 0 : POSCARs are not output.

  • 1 : POSCARs are output.