11. Calculation of thermodynamic quantities using Monte Carlo (MC) simulation¶
11.1. Theoretical backgrounds¶
Under construction.
11.2. cmc¶
- Performing canonical MC simulation.
- Available only for binary systems.
- Available for multi-thread calculations using OPENMP.
Input files
Output files
- cmc.out
- POSCAR_finish (Final atomic position)
11.3. gcmc¶
- Performing semi-grand canonical MC simulation.
- Available only for binary systems.
- Available for multi-thread calculations using OPENMP.
- Input parameters except for MU tag are the same as those used in cmc.
Input files
Output files
- gcmc.out
- POSCAR_finish (Final atomic position)
11.4. MC.in¶
An equilibration process is started from a random structure, and thermodynamic quantities are calculated at 1000 K using cmc.
ISUB = 1
ITEMP = 0
TEMP = 1000
NSTEPANN = 2000
NSTEPEQV = 2000
NUCELL = 10 10 10
SPIN = 1 -1
IPOS = 0
COMP = 3 1
Starting from the structure specified by POSCAR, a thermodynamic equilibration process is performed by decreasing temperature gradually from 10000 K to 1000 K. Thermodynamic quantities are calculated at 1000 K using gcmc.
ISUB = 1
ITEMP = 1
TEMPINIT = 10000
TEMPFINAL = 1000
TEMPMUL = 0.95
NSTEPANN = 2000
NSTEPEQV = 2000
NUCELL = 10 10 10
SPIN = 1 -1
IPOS = 1
NUCELLPOSCAR = 2 1 1
NAMEPOT = Mg Zn
MU = 0.200
11.4.1. ISUB tag¶
Sublattice indexes for performing the CE. The CE is performed on ISUBth lattice sites of UPOSCAR (line 6).
- Default : 1
- Example : ISUB = 1 3
11.4.2. ITEMP tag¶
ITEMP tag determines how to set temperatures.
- Setting temperatures manually.
- Automatic setting of temperatures using an exponential function
- Automatic setting of temperatures using an logarithmetic function
- Default : 0
- Example : ITEMP = 1
11.4.3. TEMP tag¶
Temperatures for ITEMP = 0. Thermodynamic quantities are calculated at the final temperature.
- Default : none
- Example : TEMP = 1000 900 800
11.4.4. TEMPINIT tag, TEMPFINAL tag¶
Initial and final temperatures for TEMP = 1 or 2. Thermodynamic quantities are calculated at the final temperature.
- Default : none
- Example : TEMPINIT = 5000
- Example : TEMPFINAL = 1000
11.4.5. TEMPMUL tag¶
Exponential base used in the automaic setting of temperatures for ITEMP = 1. Set values ranged from 0 to 1.
- Default : none
- Example : TEMPMUL = 0.95
11.4.6. NSTEPANN tag¶
Number of steps per atom for performing equilibration.
- Default : none
- Example : NSTEPANN = 2000
11.4.7. NSTEPEQV tag¶
Number of steps per atom for calculating thermodynamic quantities.
- Default : none
- Example : NSTEPEQV = 2000
11.4.8. NUCELL tag¶
MC simulation is performed using a supercell constructed by the NUCELL expansion of the unit cell. The supercell can only be constructed by an isotropical expansion.
- Default : none
- Example : NUCELL = 10 10 10
11.4.9. IPOS tag¶
IPOS tag determines how to prepare the initial structure.
- Random structure. The composition of the random structure is needed to be specified by COMP tag.
- Initial structure is prepared by POSCAR and POTCAR. NAMEPOT, SPIN and NUCELLPOSCAR tags are needed.
- Default : 0
- Example : IPOS = 1
11.4.10. SPIN tag¶
Spin values of atoms. In binary systems, SPIN tag has two kinds of values. The same correspondence between spins and atom types used in correlation should be used here.
- Default : none
- Example : SPIN = 1 -1
11.4.11. COMP tag¶
Composition for the initial structure. (IPOS = 0)
- Default : none
- Example : COMP = 2 1
- Example : SPIN = 1 -1
In the above example, MC simulation is started from a random structure with 2(spin=+1):1(spin=-1) composition.
11.4.12. NAMEPOT tag¶
Atom names (IPOS = 1). Do not set spin values for atoms which are not used for the CE.
- Default : none
- Example : NAMEPOT = Mg Zn O
- Example : SPIN = 1 -1
In the above example, spin values for Mg and Zn are 1 and -1, respectively.
11.4.13. NUCELLPOSCAR tag¶
Number of unit cells included in POSCAR (IPOS = 1).
- Default : none
- Example : NUCELLPOSCAR = 2 1 1
11.4.14. MU tag¶
Difference of chemical potentials for gcmc.
- Default : none
- Example : MU = 0.2
MU = mu(spin1) - mu(spin2).