[QE-users] Large difference between lattice structure simulated by pwscf code and cp.x code
Jie Peng
jiepeng at umd.edu
Thu Apr 5 19:39:54 CEST 2018
Stefano:
I think that is right on the spot! Let me do a calculation using Gamma
point only in pwscf and then compare again.
So for cp.x, in order to get an accurate lattice structure, one would have
to use a n*n*n supercell instead of a unit cell since it can only process
real wavefunctions that are located at Gamma point only. Computations done
on a single unit cell using cp.x code, therefore usually produces results
that are unphysical. Is this the correct way to interpretate?
Thank you very much!
Best
Jie
On Thu, Apr 5, 2018 at 2:22 AM, Stefano de Gironcoli <degironc at sissa.it>
wrote:
> 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
>
>
>
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--
------------------------------------------------------------------------------------------------------------------------
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
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