[QE-users] Large difference between lattice structure simulated by pwscf code and cp.x code
Stefano de Gironcoli
degironc at sissa.it
Thu Apr 5 08:22:48 CEST 2018
Dear Jie Peng,
the cp.x code assumes gamma point sampling and does not process your
k-point definition card, while pw.x is using, a rather dense, grid of
points in the BZ.
I think this is the most relevant difference in your two inputs.
To see if this is the case you can repeat the pw.x calculation with
K_POINT Gamma
Is the 10 8 8 grid really necessary ? is the system metallic ?
if not I guess a smaller grid (like 6 4 4 or less) could be
sufficient and then you could use the cp.x code with a corresponding
supercell if you wish so.
stefano
On 05/04/2018 04:16, Jie Peng wrote:
> Dear all Quantum Espresso users:
>
> I have used pw.x and cp.x code to compute equilibrium lattice
> structure of 1T-HfS2 (Halfnium Disulfide) respectively, and I find
> that they give very different results.
>
> *For pwscf simulation, the input file are given below.*
> /&control/
> / calculation='vc-relax',/
> /! restart_mode='from_scratch',/
> / tstress = .true./
> / tprnfor = .true./
> //
> / wf_collect=.true./
> / etot_conv_thr=1e-6/
> / forc_conv_thr=1e-5/
> / prefix='Hf',/
> / pseudo_dir='/potential'/
> / outdir='./tmp/',/
> / //
> / &system/
> / ibrav= 4,/
> / a=3.6529/
> / c=5.6544/
> / nat= 3, ntyp= 2,/
> / ecutwfc =50/
> / vdw_corr='DFT-D',/
> / ! lspinorb=.true./
> / ! noncolin=.true./
> / ! ecutrho=300/
> / ! nbnd=14/
> /! occupations='smearing'/
> /! smearing='gaussian'/
> /! degauss=0.01/
> / ! nspin=2/
> / ! starting_magnetization(1)=0.1/
> ///
> / &electrons/
> / conv_thr=1e-12/
> / mixing_beta = 0.7/
> ///
> / &ions/
> / ion_dynamics = 'bfgs'/
> / //
> / &cell/
> / cell_dynamics = 'bfgs'/
> //
> ///
> /ATOMIC_SPECIES/
> / Hf 95.94 Hf.pbe-mt_fhi.UPF/
> / S 32.065 S.pbe-mt_fhi.UPF/
> /ATOMIC_POSITIONS (crystal)/
> /Hf -0.000000000 -0.000000000 -0.000000000/
> /S 0.666666667 0.333333333 0.257234636/
> /S 0.333333333 0.666666667 -0.257234636/
> / K_POINTS automatic/
> /10 8 8 0 0 0/
>
> The relaxed lattice structure is the one included in this input file
> (I first did the full relaxation after which I copied the resulting
> relaxed lattice structure into this input file, then modified this
> file to compute electronic structure and phonons). The forces acting
> on atoms are small and I believe this should be the equilibrium
> structure of 1T-HfS2.
>
> / Forces acting on atoms (Ry/au):/
> /
> /
> / atom 1 type 1 force = 0.00000000 0.00000000 0.00000000/
> / atom 2 type 2 force = 0.00000000 0.00000000 -0.00001404/
> / atom 3 type 2 force = -0.00000000 0.00000000 0.00001404/
> /
> /
> / Total force = 0.000020 Total SCF correction = 0.000001/
> /
> /
> /
> /
> / entering subroutine stress .../
> /
> /
> / total stress (Ry/bohr**3) (kbar) P= -0.16/
> / -0.00000129 -0.00000000 0.00000000 -0.19 -0.00 0.00/
> / -0.00000000 -0.00000129 0.00000000 -0.00 -0.19 0.00/
> / 0.00000000 0.00000000 -0.00000078 0.00 0.00 -0.12/
> /
> /
> *For cp.x, *I carefully follow the steps required to carry out a CP
> simulations: Relax electronic structure to ground state -> Relax the
> ion positions -> relax the cells. The input files are attached below.
>
> *Electronic relaxation*
> /&control/
> / calculation='cp',/
> / title='Halfnium disulfide'/
> / restart_mode='from_scratch',/
> / ndr=50,/
> / ndw=50,/
> / nstep=10000,/
> / iprint=100/
> / isave=100,/
> / tstress = .true./
> / tprnfor = .true./
> / dt=10,/
> / wf_collect=.true./
> / etot_conv_thr=1e-6/
> / forc_conv_thr=1e-3/
> / ekin_conv_thr=1e-5/
> / prefix='HfS2',/
> / pseudo_dir='/home/jpeng/HfS2/potential'/
> / outdir='./tmp/',/
> / //
> / &system/
> / ibrav= 4,/
> / a=3.6529/
> / c=5.6544/
> / nat= 3, ntyp= 2,/
> / ecutwfc =50/
> / vdw_corr='DFT-D',/
> / ! lspinorb=.true./
> / ! noncolin=.true./
> / ! ecutrho=300/
> / ! nbnd=14/
> /! occupations='smearing'/
> /! smearing='gaussian'/
> /! degauss=0.01/
> / ! nspin=2/
> / ! starting_magnetization(1)=0.1/
> /! Hf 95.94 Hf.pbe-mt_fhi.UPF/
> /! S 32.065 S.pbe-mt_fhi.UPF/
> ///
> / &electrons/
> / electron_dynamics='damp'/
> /! electron_velocities='zero'/
> / emass=400/
> / emass_cutoff=1/
> / electron_damping=0.1/
> ///
> / &ions/
> / ion_dynamics = 'none'/
> / //
> / &cell/
> / cell_dynamics = 'none'/
> //
> ///
> /ATOMIC_SPECIES/
> / Hf 95.94 Hf.pbe-mt_fhi.UPF/
> / S 32.065 S.pbe-mt_fhi.UPF/
> /ATOMIC_POSITIONS (crystal)/
> /Hf -0.000000000 -0.000000000 -0.000000000/
> /S 0.666666667 0.333333333 0.257234636/
> /S 0.333333333 0.666666667 -0.257234636/
> / K_POINTS automatic/
> /10 8 8 0 0 0/
>
> Ion relaxation
> /&control/
> / calculation='cp',/
> / title='Halfnium disulfide'/
> / restart_mode='restart',/
> / ndr=50,/
> / ndw=51,/
> / nstep=50000,/
> / iprint=100/
> / isave=100,/
> / tstress = .true./
> / tprnfor = .true./
> / dt=10,/
> / wf_collect=.true./
> / etot_conv_thr=1e-6/
> / forc_conv_thr=1e-3/
> / ekin_conv_thr=1e-5/
> / prefix='HfS2',/
> / pseudo_dir='/home/jpeng/HfS2/potential'/
> / outdir='./tmp/',/
> / //
> / &system/
> / ibrav= 4,/
> / a=3.6529/
> / c=5.6544/
> / nat= 3, ntyp= 2,/
> / ecutwfc =50/
> / vdw_corr='DFT-D',/
> / ! lspinorb=.true./
> / ! noncolin=.true./
> / ! ecutrho=300/
> / ! nbnd=14/
> /! occupations='smearing'/
> /! smearing='gaussian'/
> /! degauss=0.01/
> / ! nspin=2/
> / ! starting_magnetization(1)=0.1/
> /! Hf 95.94 Hf.pbe-mt_fhi.UPF/
> /! S 32.065 S.pbe-mt_fhi.UPF/
> ///
> / &electrons/
> / electron_dynamics='damp'/
> /! electron_velocities='zero'/
> / emass=400/
> / emass_cutoff=1/
> / electron_damping=0.1/
> ///
> / &ions/
> / ion_dynamics = 'damp'/
> / ion_damping=0.1/
> / ion_nstepe=10/
> / //
> / &cell/
> / cell_dynamics = 'none'/
> //
> ///
> /ATOMIC_SPECIES/
> / Hf 95.94 Hf.pbe-mt_fhi.UPF/
> / S 32.065 S.pbe-mt_fhi.UPF/
> /ATOMIC_POSITIONS (crystal)/
> /Hf -0.000000000 -0.000000000 -0.000000000/
> /S 0.666666667 0.333333333 0.257234636/
> /S 0.333333333 0.666666667 -0.257234636/
> / K_POINTS automatic/
> /10 8 8 0 0 0/
>
> Cell relaxation
> /&control/
> / calculation='vc-cp',/
> / title='Halfnium disulfide'/
> / restart_mode='reset_counters',/
> / ndr=51,/
> / ndw=52,/
> / nstep=50000,/
> / iprint=100/
> / isave=100,/
> / tstress = .true./
> / tprnfor = .true./
> / dt=10,/
> / wf_collect=.true./
> / etot_conv_thr=1e-6/
> / forc_conv_thr=1e-3/
> / ekin_conv_thr=1e-5/
> / prefix='HfS2',/
> / pseudo_dir='/home/jpeng/HfS2/potential'/
> / outdir='./tmp/',/
> / //
> / &system/
> / ibrav= 4,/
> / a=3.6529/
> / c=5.6544/
> / nat= 3, ntyp= 2,/
> / ecutwfc =50/
> / vdw_corr='DFT-D',/
> / ! lspinorb=.true./
> / ! noncolin=.true./
> / ! ecutrho=300/
> / ! nbnd=14/
> /! occupations='smearing'/
> /! smearing='gaussian'/
> /! degauss=0.01/
> / ! nspin=2/
> / ! starting_magnetization(1)=0.1/
> /! Hf 95.94 Hf.pbe-mt_fhi.UPF/
> /! S 32.065 S.pbe-mt_fhi.UPF/
> ///
> / &electrons/
> / electron_dynamics='damp'/
> /! electron_velocities='zero'/
> / emass=400/
> / emass_cutoff=1/
> / electron_damping=0.1/
> ///
> / &ions/
> / ion_dynamics = 'damp'/
> / ion_damping=0.1/
> / ion_nstepe=10/
> / //
> / &cell/
> / cell_dynamics = 'pr'/
> /! cell_damping=0.1/
> /! cell_dofree=volume/
> ///
> /ATOMIC_SPECIES/
> / Hf 95.94 Hf.pbe-mt_fhi.UPF/
> / S 32.065 S.pbe-mt_fhi.UPF/
> /ATOMIC_POSITIONS (crystal)/
> /Hf -0.000000000 -0.000000000 -0.000000000/
> /S 0.666666667 0.333333333 0.257234636/
> /S 0.333333333 0.666666667 -0.257234636/
> / K_POINTS automatic/
> /10 8 8 0 0 0/
>
> The final equilibrium lattice structure obtained by cp.x is:
> **/ CELL_PARAMETERS/
> / 8.27944202 -3.49986616 -1.28541441/
> / 0.43381045 6.25063702 -0.26433640/
> / -1.81611680 -0.30736678 9.28229385/
> /
> /
> / System Density [g/cm^3] : 3.7550323993/
> /
> /
> /
> /
> / System Volume [A.U.^3] : 477.6950599279/
> /
> /
> /
> /
> / Center of mass square displacement (a.u.): 0.271737/
> /
> /
> / Total stress (GPa)/
> / -0.00003957 0.00000336 0.00017132/
> / 0.00000336 -0.00001393 0.00003875/
> / 0.00017132 0.00003875 0.00048005/
> / ATOMIC_POSITIONS/
> / Hf -0.57392945538368E+00 -0.32523714658422E+00
> -0.78842946683202E-01/
> / S 0.61817237992192E+01 0.34715217744206E+01
> 0.20852180260292E+00/
> / S 0.31507619982481E+00 0.41860506478142E+01
> -0.20961035507250E+01/
> /
> /
> / ATOMIC_VELOCITIES/
> / Hf -0.49417894612947E-07 -0.41246570825668E-07
> -0.28182774835127E-06/
> / S 0.29443574450584E-06 0.17988901894696E-06
> 0.34817154465079E-06/
> / S -0.14657506118618E-06 -0.56477323752712E-07
> 0.49507043808484E-06/
> /
> /
> / Forces acting on atoms (au):/
> / Hf -0.18727766763523E-03 -0.15291863668542E-03
> -0.99976280595181E-03/
> / S 0.33856074345196E-03 0.20689440901408E-03
> 0.40153992932368E-03/
> / S -0.17602213243772E-03 -0.68887225779463E-04
> 0.57298561574671E-03/
> /
> /
> A visualization is attached here
>
>
> while by pwscf, the equilibrium lattice structure is:
> / CELL_PARAMETERS/
> / 6.90298059 -3.45149030 0.00000000/
> / 0.00000000 5.97815655 0.00000000/
> / 0.00000000 0.00000000 10.68526745/
> /
> /
> / System Density [g/cm^3] : 4.0679453101/
> /
> /
> /
> /
> / System Volume [A.U.^3] : 440.9499858676/
> /
> /
> /
> /
> / Center of mass square displacement (a.u.): 0.000000/
> /
> /
> / Total stress (GPa)/
> / 32.06481501 -0.01335027 -0.00956254/
> / -0.01335027 32.07951164 -0.00592770/
> / -0.00956139 -0.00592704 2.04176052/
> / ATOMIC_POSITIONS/
> / Hf 0.00000000000000E+00 -0.00000000000000E+00
> -0.00000000000000E+00/
> / S 0.34514902988605E+01 0.19927188491672E+01
> 0.27486208819801E+01/
> / S -0.34514902047533E-08 0.39854377043125E+01
> -0.27486208819801E+01/
> /
> /
> / ATOMIC_VELOCITIES/
> / Hf 0.00000000000000E+00 0.00000000000000E+00
> 0.00000000000000E+00/
> / S 0.00000000000000E+00 0.00000000000000E+00
> 0.00000000000000E+00/
> / S 0.00000000000000E+00 0.00000000000000E+00
> 0.00000000000000E+00/
> /
> /
> / Forces acting on atoms (au):/
> / Hf 0.70847502228925E-03 0.43071957102166E-03
> -0.17703368862259E-04/
> / S -0.52668423530029E-03 -0.28607208606422E-03
> -0.81547327015321E-01/
> / S -0.41998284595312E-03 -0.22039679837681E-03
> 0.81837284893753E-01/
>
> A visulization is attached below
>
>
>
> I am expecting some difference because pw.x uses DFT and BFGS
> algorithm to relax the lattice structure while cp.x uses CP method,
> but not so large a difference. Especially since the lattice structure
> given by pw.x agrees with experiments and other published works, I am
> suspecting is it because I have not correctly carried out variable
> cell CP simulations.
>
> Can anyone help me understand the discrepancy I see in the results
> produced by pw.x and cp.x code? Or pointing out any mistake I have
> made during my simulations?
>
> Thank you in advance for your help, sincerely!
>
> Best
> Jie
> --
> ------------------------------------------------------------------------------------------------------------------------
> Jie Peng
> PhD student
> 2134 Glenn Martin Hall, Mechanical Engineering, University of Maryland
> College Park, Maryland, USA
> Phone:(+1) 240-495-9445
> Email: jiepeng at umd.edu <mailto:jiepeng at umd.edu>
>
>
>
> _______________________________________________
> users mailing list
> users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
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