VASP Modifications

There are various modifications of VASP on the cluster, and others that are available but not installed on the cluster.

• Spin-orbit coupling: Installed as vasp_5.2_intel-parallel_so

• Selective relaxation: Modify the file constr_cell_relax.f90 to change the stress tensor. For example, there’s an executable with “isif27” that relaxes ions and volume, while keeping the shape constant; the stress tensor is forced to be a diagonal matrix with uniform diagonal elements.

  Note: ISIF=7 relaxes volume and not using the code (in main.F)

  IF (DYN%ISIF==7) THEN
     DO I=1,3
     DO J=1,3
        D2SIF(J,I)=0
     ENDDO
     D2SIF(I,I)=PRESS*FACTSI
     ENDDO
  ENDIF
  

  The value of PRESS is calculated (in force.F) by

  PRESS=(TSIF(1,1)+TSIF(2,2)+TSIF(3,3))/3._q &
       &      -DYN%PSTRESS/(EVTOJ*1E22_q)*LATT_CUR%OMEGA
  

  Where TSIF and D2SIF are related by (in main.F)

  D2SIF(I,K)=TSIF(I,K)*FACTSI
  

  These are different only if

  Therefore, there is a difference between using the stress tensor based on the pressure vs. using it as a diagonal matrix with a=b=c; this difference is -DYN%PSTRESS/(EVTOJ*1E22_q)*LATT_CUR%OMEGA

  Iff PSTRESS=0, then this makes no difference. Beware.