Why 'vc-relax' option in QE does not optimize lattice parameters?

Krishnamoorthy Arumugam @Krishnamoorthy-Arumugam

14 November 2019 2 2K Report

I tried to do optimization for my system with QE (ubuntu). The input file is below.

&CONTROL

title = 'OPT' ,

calculation = 'vc-relax' ,

restart_mode = 'from_scratch' ,

outdir = './' ,

pseudo_dir = './' ,

prefix = 'test' ,

verbosity='high',

&SYSTEM

ibrav =1

celldm(1)= 11.88395853

nat =9

ntyp =5

ecutwfc =60.0 ,

ecutrho =240.0 ,

nspin=1, ! default is 1 which refers to non-polarized calculation

&ELECTRONS

electron_maxstep = 500,

conv_thr = 1.0e-6 ,

&IONS

ion_dynamics = 'bfgs'

&CELL

cell_dynamics = 'bfgs',

cell_dofree = 'all', ! all axis and angles are moved

cell_factor = 4.5,

ATOMIC_SPECIES

ATOMIC_POSITIONS {alat}

K_POINTS automatic

10 10 10 0 0 0

I have managed to get convergence. However, the lattice has been fixed throughout the optimization calculation.

>grep alat= case.out

CELL_PARAMETERS (alat= 11.88395853)

How can I solve this issue?

Michael Wolloch

Hi,

Could it be that the cell is indeed changed, but in the output the scaling factor alat is still constant?"

Have you looked at the CELL_PARAMETERS card at the end of your output file after "Begin final coordinates" and compared them to the initial values?

I have not used QE in a while, but at least in VASP the scaling parameter (alat here) stays constant and the lattice vectors change.

Cheers, M

Krishnamoorthy Arumugam

Thank you for your reply. I have checked the CELL PARAMETERS. The final parameters are different from the initial input.

Best regards,

KRISH

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