[Pw_forum] vc-relax (not orthogonal operation)

[Sohail Ahmad]

Dear QE users,
I am using vc-relax first time to get the optimised structure of MoS2 monolayer.
I believe the symmetry is breaking in the second step due to relaxation in x and y direction it is changing the number of k-points.

What is the solution ??? (Somebody suggested a bigger cell with orthorhombic cell)
But HOW and WHY ???

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Error in routine checkallsym (2):
not orthogonal operation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

stopping ...
-----------------------------------------------------------------------------------------------------------------------
input file as below

&control
calculation = 'vc-relax',
restart_mode = 'from_scratch',
etot_conv_thr = 1.0d-5,
forc_conv_thr = 1.0d-4,
tstress = '.true.',
tprnfor = '.true.,
prefix = 'MoSml',
pseudo_dir = '/home/sohail/Espresso/espresso-5.0.1/pseudo',
outdir = './OUT',
/
&system
ibrav = 4, a = 3.16, b = 3.16, c = 15, cosac = 0.0, cosbc = 0.0, cosab = -0.5,
nat = 3, ntyp = 2,
ecutwfc = 70,
ecutrho = 300,
nbnd = 26,
occupations = 'smearing', smearing = 'gaussian', degauss = 0.001,
nspin = 2,
starting_magnetization(1) = 0.1d0,
/
&electrons
mixing_beta = 0.7d0,
conv_thr = 1.0d-15,
electron_maxstep = 500,
/
&ions
ion_dynamics = 'bfgs',
/
&cell
cell_dynamics = 'bfgs',
press = 0.d0,
press_conv_thr = 1.2d0,
cell_dofree = 'xy',
/
ATOMIC_SPECIES
Mo 95.96 Mo.pw91-n-van.UPF
S 32.06 S.pw91-van_ak.UPF
ATOMIC_POSITIONS {Angstrom}
Mo -0.000000016 1.824426860 3.072500000
S 1.580000016 0.912213416 1.474800000
S 1.580000016 0.912213416 4.670200000
K_POINTS {AUTOMATIC}
8 8 1 0 0 0


Thanks
Sohail Ahmad
King Khalid University
Abha, Saudi Arabia

[Bahadır salmankurt]

Dear Sohail Ahmad

using *nosym=.true*. in &system can solve the problem. But I dont know it
is suitable or not.

Regards

Post by Sohail Ahmad
Dear QE users,
I am using vc-relax first time to get the optimised structure of MoS2 monolayer.
I believe the symmetry is breaking in the second step due to relaxation in
x and y direction it is changing the number of k-points.
What is the solution ??? (Somebody suggested a bigger cell with orthorhombic cell)
But HOW and WHY ???
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
not orthogonal operation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
stopping ...
-----------------------------------------------------------------------------------------------------------------------
input file as below
&control
calculation = 'vc-relax',
restart_mode = 'from_scratch',
etot_conv_thr = 1.0d-5,
forc_conv_thr = 1.0d-4,
tstress = '.true.',
tprnfor = '.true.,
prefix = 'MoSml',
pseudo_dir = '/home/sohail/Espresso/espresso-5.0.1/pseudo',
outdir = './OUT',
/
&system
ibrav = 4, a = 3.16, b = 3.16, c = 15, cosac = 0.0, cosbc = 0.0, cosab = -0.5,
nat = 3, ntyp = 2,
ecutwfc = 70,
ecutrho = 300,
nbnd = 26,
occupations = 'smearing', smearing = 'gaussian', degauss = 0.001,
nspin = 2,
starting_magnetization(1) = 0.1d0,
/
&electrons
mixing_beta = 0.7d0,
conv_thr = 1.0d-15,
electron_maxstep = 500,
/
&ions
ion_dynamics = 'bfgs',
/
&cell
cell_dynamics = 'bfgs',
press = 0.d0,
press_conv_thr = 1.2d0,
cell_dofree = 'xy',
/
ATOMIC_SPECIES
Mo 95.96 Mo.pw91-n-van.UPF
S 32.06 S.pw91-van_ak.UPF
ATOMIC_POSITIONS {Angstrom}
Mo -0.000000016 1.824426860 3.072500000
S 1.580000016 0.912213416 1.474800000
S 1.580000016 0.912213416 4.670200000
K_POINTS {AUTOMATIC}
8 8 1 0 0 0
Thanks
Sohail Ahmad
King Khalid University
Abha, Saudi Arabia
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[Paolo Giannozzi]

Post by Sohail Ahmad
cell_dofree = 'xy'

you cannot use this option: it breaks hexagonal symmetry.

Paolo