[QE-users] Energy not decreasing when running vc-relax calculation with 'r2scan' functional

[陈科帆]

Hi there,




Thank you for your previous help on ld1.x! Also, I found a pseudopotential set with atomic orbital included, pseudo-dojo.




I'm now trying to relax TiO2 and hcp-Ti with nc-pp from pseudo-dojo, running 'r2scan' functional.




However, I always observe an energy increase in the relaxation steps. Meanwhile, the stress on the cell is not getting smaller. I've tried different versions of pseudopotentials from pseudo-dojo(v0.4, pbe, pw and pbesol). The problem persists. My input file is at the end of this email. You'll also find output energy and stress after the input file. I'm quite new using a non-pbe functional so I'm not sure which input parameter I should look into.




Thank you so much for your help!




Kefan




INPUT:

&control

calculation='vc-relax',

prefix='TiO2_dojo_relax'

outdir='./output_TiO2_dojo'

pseudo_dir='./dojo04_pw_high'

/

&system

ibrav=6,

celldm(1)=8.532654,

celldm(3)=0.672853,

nat=6,ntyp=2,

ecutwfc=400,

occupations='smearing',

smearing='gaussian',

degauss=0.02,

input_dft='r2scan',

exxdiv_treatment='gygi-baldereschi',

ecutvcut=0.4,

nqx1=4,nqx2=4,nqx3=4

/

&electrons

mixing_beta=0.1,

electron_maxstep=300,

/

&ions

/

&cell

cell_dynamics='bfgs'

/

ATOMIC_SPECIES

Ti 47.867 Ti.upf

O 15.999 O.upf

ATOMIC_POSITIONS (crystal)

Ti     0.500000         0.500000         0.500000

Ti     0.000000         0.000000         0.000000

O     0.200764         0.799236         0.500000

O     0.799236         0.200764         0.500000

O     0.700764         0.700764         0.000000

O     0.299236         0.299236         0.000000

K_POINTS (automatic)

8 8 8 0 0 0




An example of output energy: (This is part of the whole relaxation output, the rest part is similar to what's shown here)

!    total energy              =    -360.68407951 Ry

!    total energy              =    -360.36055154 Ry

!    total energy              =    -360.59563090 Ry

!    total energy              =    -360.66225311 Ry

!    total energy              =    -360.67925379 Ry

!    total energy              =    -360.68326714 Ry

!    total energy              =    -360.68408962 Ry

!    total energy              =    -360.68419620 Ry

!    total energy              =    -360.68412678 Ry

!    total energy              =    -360.68408658 Ry

!    total energy              =    -360.68406230 Ry

Example of output stress:
          total   stress  (Ry/bohr**3)                   (kbar)     P=     9235.88
   0.06306395   0.00000000   0.00000000         9277.03        0.00        0.00
   0.00000000   0.06306395   0.00000000            0.00     9277.03        0.00
   0.00000000   0.00000000   0.06222474            0.00        0.00     9153.58
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     6003.45
   0.04105619   0.00000000   0.00000000         6039.57        0.00        0.00
   0.00000000   0.04105619   0.00000000            0.00     6039.57        0.00
   0.00000000   0.00000000   0.04031941            0.00        0.00     5931.19
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     7389.65
   0.05050933   0.00000000   0.00000000         7430.18        0.00        0.00
   0.00000000   0.05050933   0.00000000            0.00     7430.18        0.00
   0.00000000   0.00000000   0.04968288            0.00        0.00     7308.60
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     8245.72
   0.05633717   0.00000000   0.00000000         8287.48        0.00        0.00
   0.00000000   0.05633717   0.00000000            0.00     8287.48        0.00
   0.00000000   0.00000000   0.05548546            0.00        0.00     8162.19
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     8723.04
   0.05958080   0.00000000   0.00000000         8764.64        0.00        0.00
   0.00000000   0.05958080   0.00000000            0.00     8764.64        0.00
   0.00000000   0.00000000   0.05873251            0.00        0.00     8639.85
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     8974.70
   0.06129011   0.00000000   0.00000000         9016.09        0.00        0.00
   0.00000000   0.06129011   0.00000000            0.00     9016.09        0.00
   0.00000000   0.00000000   0.06044601            0.00        0.00     8891.91
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     9103.60
   0.06216601   0.00000000   0.00000000         9144.94        0.00        0.00
   0.00000000   0.06216601   0.00000000            0.00     9144.94        0.00
   0.00000000   0.00000000   0.06132295            0.00        0.00     9020.92
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     9170.12
   0.06261743   0.00000000   0.00000000         9211.34        0.00        0.00
   0.00000000   0.06261743   0.00000000            0.00     9211.34        0.00
   0.00000000   0.00000000   0.06177676            0.00        0.00     9087.67
--
          total   stress  (Ry/bohr**3)                   (kbar)     P=     9202.74
   0.06283894   0.00000000   0.00000000         9243.93        0.00        0.00
   0.00000000   0.06283894   0.00000000            0.00     9243.93        0.00
   0.00000000   0.00000000   0.06199889            0.00        0.00     9120.35
















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