[QE-users] Large difference between lattice structure simulated by pwscf code and cp.x code
Jie Peng
jiepeng at umd.edu
Thu Apr 5 04:16:11 CEST 2018
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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