My Community

Hello. I am trying to compute simple lattice constants for bulk GaN using sX-LDA but I keep having this error tag before my first ionic relaxation step:

"Stress not implemented
Stress not implemented
Stress not implemented
Stress not implemented
Stress not implemented
Stress not implemented
Stress not implemented"

I am a lot more experienced using HSE06 and it appears that this error is probably related to Pulay stresses. I have increased my cutoff energy and the precision -tag but nothing seems to work so far. Here are some of my INCAR parameters for the sx-LDA calculation:

LHFCALC = .TRUE. !Hybrid functionals
LTHOMAS = .TRUE. ; HFSCREEN = 1.8 ! standard Thomas-Fermi(TF) wavevector length for semiconductors
AEXX = 1.0 ! amount of exact exchange different than 0.25 in regular HSE03 HSE06
ALDAC = 1.0 ! the fraction of LDA correlation in a Hartree-Fock/DFT hybrid functional
NBANDS = 16 !number of occupied bands, I may need more bands than that

PREC = High
ISPIN = 1
ALGO = All ; TIME = 0.4
LREAL= .FALSE. !Auto for supercells and false for small cells
ISMEAR = 0 ! 0=Gaussian, -1=Fermi,-4,-5=tetra, 1-5=M-P order
SIGMA = 0.05
ISIF = 4 ! keep volume constant for primitive unit cell

I am pretty sure my mistake is coming from either my AEXX and ALDAC tags. Here I am not quite sure if
1. for 100% HF exchange screened with the TF vector, is VASP automatically using the LDA correlation or one has to enter the ALDAC tag?
2. is it physically acceptable to add a PBE correlation (with PBE potentials of course) to the sX although the TF wave vector was derived from the uniform electron gas theory?

Hi,

We're sorry that we didn’t answer your question. This does not live up to the quality of support that we aim to provide. The team has since expanded. If we can still help with your problem, please ask again in a new post, linking to this one, and we will answer as quickly as possible.

Best wishes,

VASP