not “unphysical” just inaccurate … SB
> On 5 Apr 2018, at 19:39, Jie Peng <jiep...@umd.edu> wrote: > > 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 <degir...@sissa.it > <mailto:degir...@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 >> <image.png> >> >> 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 >> <image.png> >> >> >> 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: jiep...@umd.edu <mailto:jiep...@umd.edu> >> >> >> >> _______________________________________________ >> users mailing list >> users@lists.quantum-espresso.org <mailto:users@lists.quantum-espresso.org> >> https://lists.quantum-espresso.org/mailman/listinfo/users >> <https://lists.quantum-espresso.org/mailman/listinfo/users> > > _______________________________________________ > users mailing list > users@lists.quantum-espresso.org <mailto:users@lists.quantum-espresso.org> > https://lists.quantum-espresso.org/mailman/listinfo/users > <https://lists.quantum-espresso.org/mailman/listinfo/users> > > > > -- > ------------------------------------------------------------------------------------------------------------------------ > Jie Peng > PhD student > 2134 Glenn Martin Hall, Mechanical Engineering, University of Maryland > College Park, Maryland, USA > Phone:(+1) 240-495-9445 > Email: jiep...@umd.edu <mailto:jiep...@umd.edu> > > _______________________________________________ > users mailing list > users@lists.quantum-espresso.org > https://lists.quantum-espresso.org/mailman/listinfo/users
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