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Posted: **Mon Jul 24, 2006 6:26 pm**

Dear VASPmaster,

I have a simple question. I want to calculate the contribution
of the electrons kinetic energy, ie:

Â Â Â Â Â Â Â Â Â Â Â Â Â h^2Â Â Â NÂ Â Â Â Â Â Â Â Â *Â Â Â Â Â Â Â 2Â Â Â Â 
Â TÂ Â Â Â =Â -Â Â ---Â Â SumÂ Â <PsiÂ |gradÂ |Psi>
Â Â Â Â Â Â Â Â Â Â Â Â Â 2Â mÂ Â i=1Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â

where N is the total number of electrons.

I found out that in the file elf.F is actually calculated.
So I just averaged it and multiplied it with the volume of the
system (see below). The result that I get I think is in eV.
Are all these correct or am I totally wrong?

Thank you very much!!

PS: Of course in the INCAR file I set: LELF = .TRUE.

Part of the elf.F file:

Code: Select all

Â Â Â Â Â Â SUBROUTINEÂ ELFCAL(CHDEN,LAPLAC,CKINE,CGRDSQ,GRID,LATT_CUR)
Â Â Â Â Â Â USEÂ prec
Â Â Â Â Â Â USEÂ mpimy
Â Â Â Â Â Â USEÂ mgrid
Â Â Â Â Â Â USEÂ constant
Â Â Â Â Â Â USEÂ lattice
Â Â Â Â Â Â IMPLICITÂ COMPLEX(q)Â (C)
Â Â Â Â Â Â IMPLICITÂ REAL(q)Â (A-B,D-H,O-Z)

Â Â Â Â Â Â TYPEÂ (grid_3d)Â GRID
Â Â Â Â Â Â TYPEÂ (latt)Â Â Â Â Â Â Â Â LATT_CUR

Â Â Â Â Â Â RGRIDÂ CHDEN(GRID%RL%NP),CKINE(GRID%RL%NP),CGRDSQ(GRID%RL%NP)
Â Â Â Â Â Â RGRIDÂ LAPLAC(GRID%RL%NP)
!===========================================
!Â Â calculateÂ ELFÂ (e.g.:Â Nature,Â 371(1994)683-686)
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â _
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â h^2Â Â Â Â *Â Â Â Â 2Â Â Â Â Â Â Â Â Â T.........kineticÂ energy
!Â TÂ Â Â Â =Â -Â 2Â ---Â PsiÂ gradÂ PsiÂ Â Â T+TCORR...pos.definiteÂ kineticÂ energy
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2Â mÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â TBOS......TÂ ofÂ anÂ idealÂ Bose-gas
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â _Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â (=infimumÂ ofÂ T+TCORR)
!Â Â Â Â Â Â Â Â Â Â Â Â Â 1Â h^2Â Â Â Â Â Â 2Â Â Â Â Â Â Â Â Â Â Â DH........TÂ ofÂ hom.non-interact.e-Â -Â gas
!Â TCORR=Â -Â ---Â Â gradÂ rhoÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â (acc.toÂ Fermi)
!Â Â Â Â Â Â Â Â Â Â Â Â Â 2Â 2Â mÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ELF.......electron-localization-function
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â _Â Â Â Â Â Â Â Â Â Â Â Â Â 2
!Â Â Â Â Â Â Â Â Â Â Â Â Â 1Â h^2Â |gradÂ rho|
!Â TBOSÂ =Â -Â ---Â ----------Â Â Â Â Â Â Â DÂ =Â TÂ +Â TCORRÂ -Â TBOS
!Â Â Â Â Â Â Â Â Â Â Â Â Â 4Â 2Â mÂ Â Â Â rho
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â _Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â \Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 1
!Â Â Â Â Â Â Â Â Â Â Â Â 3Â h^2Â Â Â Â Â Â Â Â 2/3Â Â 5/3Â Â Â Â Â Â Â Â Â Â =====>Â Â Â Â ELFÂ =Â ------------
!Â DHÂ Â Â =Â -Â ---Â (3Â Pi^2)Â Â rhoÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â /Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â DÂ Â Â 2
!Â Â Â Â Â Â Â Â Â Â Â Â Â 5Â 2Â mÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 1Â +Â (Â ---Â )
!Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â DH
!===========================================
Â Â Â Â Â Â PISQÂ Â Â =Â PI*PI
Â Â Â Â Â Â FIVTHIÂ =Â 5._q/3._q

Â Â Â Â Â Â TtotÂ =Â 0.0d0
Â Â Â Â Â Â DOÂ N=1,GRID%RL%NP
Â Â Â Â Â Â Â TÂ Â Â Â =Â REAL(Â CKINE(N)Â ,KIND=q)
Â Â Â Â Â Â Â TtotÂ =Â TtotÂ +Â T
Â Â Â Â Â Â Â TCORR=Â REAL(Â LAPLAC(N)Â ,KIND=q)Â *HSQDTM/2._q
!Â Â Â Â Â Â write(*,*)Â "KINEÂ =Â ",Ttot,T,N,Ttot/real(N)
Â Â Â Â Â Â Â TBOSÂ =Â HSQDTM/4._q*Â REAL(Â CGRDSQ(N)/CHDEN(N)Â ,KIND=q)
Â Â Â Â Â Â Â DHÂ =Â 0.2_q*HSQDTM/PISQ*Â (3*PISQ*Â REAL(Â CHDEN(N)Â ,KIND=q)Â )**FIVTHI
Â Â Â Â Â Â Â CKINE(N)=1/(1+((T+TCORR-TBOS)/MAX(DH,1E-8_q))**2)
Â Â Â Â Â Â ENDDO
Â Â Â Â Â Â Â write(*,*)Â "KINEÂ =Â ",Ttot*LATT_CUR%OMEGA/real(N)

Â Â Â Â Â Â RETURN

Â Â Â Â Â Â END

<span class='smallblacktext'>[ Edited ]</span>

Posted: **Mon Jul 24, 2006 9:53 pm**

For pseudopotential calculations the kinetic energy is somewhat ill defined. If the phi in your equation is the pseudo-wavefunction, then you will not get the true expectation value of the kinetic energy of the actual wavefunction. This pseudo-kinetic energy is the most you can get out of vasp, as the Dij terms in the us pseudopotential combine the kinetic, coulombic, and exchange-correlation energies associated with each nonlocal projection operator. If you want the pseudo-kinetic energy, I have a modified version of vasp that will calculate it and print it in the OUTCAR file. I don't know the legalities of me sending this to you would be, though, so I would need an okay from the admin.

Posted: **Wed Jul 26, 2006 2:23 pm**

Hello,
If there is no problem (as you said) it would be great if you could sent it to me.
Thank you very much for your help.

Posted: **Wed Nov 09, 2011 8:38 pm**

Dear my friends!
I also need to calculate the electronic kinetic energy term, however, it is difficult for me to modify the code.
So, could you please also send me the modified version of vasp if it is possible?
Thanks a lot!

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Kinetic Energy Term

Kinetic Energy Term

Kinetic Energy Term

Kinetic Energy Term

Kinetic Energy Term