Cd Si relaxation

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Task

Relaxation of the internal coordinates of a perturbed cd Si structure.

Input

POSCAR

cubic diamond
   5.5
 0.0    0.5     0.5
 0.5    0.0     0.5
 0.5    0.5     0.0
  2
Direct
 -0.125 -0.125 -0.125
  0.125  0.125  0.130

• Break of symmetry in standard diamond structure: change z position from 0.125 to 0.130.

INCAR

System = diamond Si
ISTART = 0 ; ICHARG=2
ENCUT  =    240
ISMEAR = 0; SIGMA = 0.1;
NSW    =  10; IBRION =  2
ISIF   =  2
EDIFFG = -0.0001

• 10 relaxation steps (NSW=10).
• Conjugate-gradient algorithm (IBRION=2).
• Relaxation only of internal parameters (ISIF=2).

KPOINTS

k-points
 0
Monkhorst Pack
 11 11 11
 0  0  0

Calculation

• Example output after 10 relaxation steps:

POSITION                                       TOTAL-FORCE (eV/Angst)
-----------------------------------------------------------------------------------
     4.81253      4.81253      4.81250        -0.000724     -0.000724     -0.000031
     0.68747      0.68747      0.68750         0.000724      0.000724      0.000031
-----------------------------------------------------------------------------------
   total drift:                                0.000000      0.000000      0.000000

• Files to watch during relaxations:
  • stdout (terminal): each electronic step is written to the terminal:
  • OSZICAR: a copy of the terminal output.
  • OUTCAR: more detailed information on every electronic and ionic step.

• Other important files:
  • CONTCAR: holds the structure of the last ionic step and at the end the structural result (also very important for restarting a relaxation).
  • STOPCAR: stops a relaxation.

Download

diamondSirel.tgz

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