Hi friends ,i am trying to construct an Energy volume plot for delta zncl2, in order to calculate the equilibrium lattice constant.I am using the tags:
IBRION=2
ISIF=2
ISMEAR=0
PREC=High
NSW=100
I gave relaxations and re-relaxations until the CONTCAR and POSCAR files exactly matched..I then used the final TOTEN value from the OUTCAR file[without entropy] and plotted it against volume for different values of lattice constant (a,b,c i have varied c keeping the other 2 constant).
However,i am not getting an energy minimum in the region around the experimental lattice constant even though external pressure ->0 around experimental lattice constant.Energy minimum comes only around volume corresponding to ~(lattice constant+0.5) angstroms.
Have I missed a step? is something left to be done?am i reading the wrong energy value?please suggest.
The manual says i need to give a run with ISMEAR=-5 and no relaxations.Can somebody please provide the other parameters of the required INCAR file(especially ISIF)?
energy-volume minimisation
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Shreevant
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energy-volume minimisation
Last edited by Shreevant on Mon Jun 12, 2006 8:56 am, edited 1 time in total.
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admin
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energy-volume minimisation
1) automatic cell shape and volume relaxation can be done by ISIF=3
(not 2)
2) mind that the equilibrium lattice parameters depend on the chosen potential (LDA,GGA,...) type.
3) please read the accuracy.pdf tutorial (to be downloaded from the VASP-workshop site) on how to perform geometry optimizations.
(not 2)
2) mind that the equilibrium lattice parameters depend on the chosen potential (LDA,GGA,...) type.
3) please read the accuracy.pdf tutorial (to be downloaded from the VASP-workshop site) on how to perform geometry optimizations.
Last edited by admin on Tue Jun 13, 2006 1:40 pm, edited 1 time in total.