<div dir="ltr">Dear all Quantum Espresso users:<div><br></div><div>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.</div><div><br></div><div><b>For pwscf simulation, the input file are given below.</b></div><div><div><i>&control</i></div><div><i> calculation='vc-relax',</i></div><div><i>! restart_mode='from_scratch',</i></div><div><i> tstress = .true.</i></div><div><i> tprnfor = .true.</i></div><div><i> </i></div><div><i> wf_collect=.true.</i></div><div><i> etot_conv_thr=1e-6</i></div><div><i> forc_conv_thr=1e-5</i></div><div><i> prefix='Hf',</i></div><div><i> pseudo_dir='/potential'</i></div><div><i> outdir='./tmp/',</i></div><div><i> /</i></div><div><i> &system</i></div><div><i> ibrav= 4,</i></div><div><i> a=3.6529</i></div><div><i> c=5.6544</i></div><div><i> nat= 3, ntyp= 2,</i></div><div><i> ecutwfc =50</i></div><div><i> vdw_corr='DFT-D',</i></div><div><i> ! lspinorb=.true.</i></div><div><i> ! noncolin=.true.</i></div><div><i> ! ecutrho=300</i></div><div><i> ! nbnd=14</i></div><div><i>! occupations='smearing'</i></div><div><i>! smearing='gaussian'</i></div><div><i>! degauss=0.01</i></div><div><i> ! nspin=2</i></div><div><i> ! starting_magnetization(1)=0.1</i></div><div><i>/</i></div><div><i> &electrons</i></div><div><i> conv_thr=1e-12</i></div><div><i> mixing_beta = 0.7</i></div><div><i>/</i></div><div><i> &ions</i></div><div><i> ion_dynamics = 'bfgs'</i></div><div><i> /</i></div><div><i> &cell</i></div><div><i> cell_dynamics = 'bfgs'</i></div><div><i> </i></div><div><i>/</i></div><div><i>ATOMIC_SPECIES</i></div><div><i> Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i> S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>ATOMIC_POSITIONS (crystal)</i></div><div><i>Hf -0.000000000 -0.000000000 -0.000000000</i></div><div><i>S 0.666666667 0.333333333 0.257234636</i></div><div><i>S 0.333333333 0.666666667 -0.257234636</i></div><div><i> K_POINTS automatic</i></div><div><i>10 8 8 0 0 0</i></div><div><br></div><div>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.</div><div><br></div><div><div><i> Forces acting on atoms (Ry/au):</i></div><div><i><br></i></div><div><i> atom 1 type 1 force = 0.00000000 0.00000000 0.00000000</i></div><div><i> atom 2 type 2 force = 0.00000000 0.00000000 -0.00001404</i></div><div><i> atom 3 type 2 force = -0.00000000 0.00000000 0.00001404</i></div><div><i><br></i></div><div><i> Total force = 0.000020 Total SCF correction = 0.000001</i></div><div><i><br></i></div><div><i><br></i></div><div><i> entering subroutine stress ...</i></div><div><i><br></i></div><div><i> total stress (Ry/bohr**3) (kbar) P= -0.16</i></div><div><i> -0.00000129 -0.00000000 0.00000000 -0.19 -0.00 0.00</i></div><div><i> -0.00000000 -0.00000129 0.00000000 -0.00 -0.19 0.00</i></div><div><i> 0.00000000 0.00000000 -0.00000078 0.00 0.00 -0.12</i></div></div><div><i><br></i></div><div><b>For cp.x, </b>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.</div><div><br></div><div><b>Electronic relaxation</b></div><div><div><i>&control</i></div><div><i> calculation='cp',</i></div><div><i> title='Halfnium disulfide'</i></div><div><i> restart_mode='from_scratch',</i></div><div><i> ndr=50,</i></div><div><i> ndw=50,</i></div><div><i> nstep=10000,</i></div><div><i> iprint=100</i></div><div><i> isave=100,</i></div><div><i> tstress = .true.</i></div><div><i> tprnfor = .true.</i></div><div><i> dt=10,</i></div><div><i> wf_collect=.true.</i></div><div><i> etot_conv_thr=1e-6</i></div><div><i> forc_conv_thr=1e-3</i></div><div><i> ekin_conv_thr=1e-5</i></div><div><i> prefix='HfS2',</i></div><div><i> pseudo_dir='/home/jpeng/HfS2/potential'</i></div><div><i> outdir='./tmp/',</i></div><div><i> /</i></div><div><i> &system</i></div><div><i> ibrav= 4,</i></div><div><i> a=3.6529</i></div><div><i> c=5.6544</i></div><div><i> nat= 3, ntyp= 2,</i></div><div><i> ecutwfc =50</i></div><div><i> vdw_corr='DFT-D',</i></div><div><i> ! lspinorb=.true.</i></div><div><i> ! noncolin=.true.</i></div><div><i> ! ecutrho=300</i></div><div><i> ! nbnd=14</i></div><div><i>! occupations='smearing'</i></div><div><i>! smearing='gaussian'</i></div><div><i>! degauss=0.01</i></div><div><i> ! nspin=2</i></div><div><i> ! starting_magnetization(1)=0.1</i></div><div><i>! Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i>! S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>/</i></div><div><i> &electrons</i></div><div><i> electron_dynamics='damp'</i></div><div><i>! electron_velocities='zero'</i></div><div><i> emass=400</i></div><div><i> emass_cutoff=1</i></div><div><i> electron_damping=0.1</i></div><div><i>/</i></div><div><i> &ions</i></div><div><i> ion_dynamics = 'none'</i></div><div><i> /</i></div><div><i> &cell</i></div><div><i> cell_dynamics = 'none'</i></div><div><i> </i></div><div><i>/</i></div><div><i>ATOMIC_SPECIES</i></div><div><i> Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i> S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>ATOMIC_POSITIONS (crystal)</i></div><div><i>Hf -0.000000000 -0.000000000 -0.000000000</i></div><div><i>S 0.666666667 0.333333333 0.257234636</i></div><div><i>S 0.333333333 0.666666667 -0.257234636</i></div><div><i> K_POINTS automatic</i></div><div><i>10 8 8 0 0 0</i></div><div style="font-weight:bold"><br></div></div><div style="font-weight:bold">Ion relaxation</div><div><div><i>&control</i></div><div><i> calculation='cp',</i></div><div><i> title='Halfnium disulfide'</i></div><div><i> restart_mode='restart',</i></div><div><i> ndr=50,</i></div><div><i> ndw=51,</i></div><div><i> nstep=50000,</i></div><div><i> iprint=100</i></div><div><i> isave=100,</i></div><div><i> tstress = .true.</i></div><div><i> tprnfor = .true.</i></div><div><i> dt=10,</i></div><div><i> wf_collect=.true.</i></div><div><i> etot_conv_thr=1e-6</i></div><div><i> forc_conv_thr=1e-3</i></div><div><i> ekin_conv_thr=1e-5</i></div><div><i> prefix='HfS2',</i></div><div><i> pseudo_dir='/home/jpeng/HfS2/potential'</i></div><div><i> outdir='./tmp/',</i></div><div><i> /</i></div><div><i> &system</i></div><div><i> ibrav= 4,</i></div><div><i> a=3.6529</i></div><div><i> c=5.6544</i></div><div><i> nat= 3, ntyp= 2,</i></div><div><i> ecutwfc =50</i></div><div><i> vdw_corr='DFT-D',</i></div><div><i> ! lspinorb=.true.</i></div><div><i> ! noncolin=.true.</i></div><div><i> ! ecutrho=300</i></div><div><i> ! nbnd=14</i></div><div><i>! occupations='smearing'</i></div><div><i>! smearing='gaussian'</i></div><div><i>! degauss=0.01</i></div><div><i> ! nspin=2</i></div><div><i> ! starting_magnetization(1)=0.1</i></div><div><i>! Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i>! S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>/</i></div><div><i> &electrons</i></div><div><i> electron_dynamics='damp'</i></div><div><i>! electron_velocities='zero'</i></div><div><i> emass=400</i></div><div><i> emass_cutoff=1</i></div><div><i> electron_damping=0.1</i></div><div><i>/</i></div><div><i> &ions</i></div><div><i> ion_dynamics = 'damp'</i></div><div><i> ion_damping=0.1</i></div><div><i> ion_nstepe=10</i></div><div><i> /</i></div><div><i> &cell</i></div><div><i> cell_dynamics = 'none'</i></div><div><i> </i></div><div><i>/</i></div><div><i>ATOMIC_SPECIES</i></div><div><i> Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i> S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>ATOMIC_POSITIONS (crystal)</i></div><div><i>Hf -0.000000000 -0.000000000 -0.000000000</i></div><div><i>S 0.666666667 0.333333333 0.257234636</i></div><div><i>S 0.333333333 0.666666667 -0.257234636</i></div><div><i> K_POINTS automatic</i></div><div><i>10 8 8 0 0 0</i></div><div style="font-weight:bold"><br></div></div><div style="font-weight:bold">Cell relaxation</div><div><div><i>&control</i></div><div><i> calculation='vc-cp',</i></div><div><i> title='Halfnium disulfide'</i></div><div><i> restart_mode='reset_counters',</i></div><div><i> ndr=51,</i></div><div><i> ndw=52,</i></div><div><i> nstep=50000,</i></div><div><i> iprint=100</i></div><div><i> isave=100,</i></div><div><i> tstress = .true.</i></div><div><i> tprnfor = .true.</i></div><div><i> dt=10,</i></div><div><i> wf_collect=.true.</i></div><div><i> etot_conv_thr=1e-6</i></div><div><i> forc_conv_thr=1e-3</i></div><div><i> ekin_conv_thr=1e-5</i></div><div><i> prefix='HfS2',</i></div><div><i> pseudo_dir='/home/jpeng/HfS2/potential'</i></div><div><i> outdir='./tmp/',</i></div><div><i> /</i></div><div><i> &system</i></div><div><i> ibrav= 4,</i></div><div><i> a=3.6529</i></div><div><i> c=5.6544</i></div><div><i> nat= 3, ntyp= 2,</i></div><div><i> ecutwfc =50</i></div><div><i> vdw_corr='DFT-D',</i></div><div><i> ! lspinorb=.true.</i></div><div><i> ! noncolin=.true.</i></div><div><i> ! ecutrho=300</i></div><div><i> ! nbnd=14</i></div><div><i>! occupations='smearing'</i></div><div><i>! smearing='gaussian'</i></div><div><i>! degauss=0.01</i></div><div><i> ! nspin=2</i></div><div><i> ! starting_magnetization(1)=0.1</i></div><div><i>! Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i>! S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>/</i></div><div><i> &electrons</i></div><div><i> electron_dynamics='damp'</i></div><div><i>! electron_velocities='zero'</i></div><div><i> emass=400</i></div><div><i> emass_cutoff=1</i></div><div><i> electron_damping=0.1</i></div><div><i>/</i></div><div><i> &ions</i></div><div><i> ion_dynamics = 'damp'</i></div><div><i> ion_damping=0.1</i></div><div><i> ion_nstepe=10</i></div><div><i> /</i></div><div><i> &cell</i></div><div><i> cell_dynamics = 'pr'</i></div><div><i>! cell_damping=0.1</i></div><div><i>! cell_dofree=volume</i></div><div><i>/</i></div><div><i>ATOMIC_SPECIES</i></div><div><i> Hf 95.94 Hf.pbe-mt_fhi.UPF</i></div><div><i> S 32.065 S.pbe-mt_fhi.UPF</i></div><div><i>ATOMIC_POSITIONS (crystal)</i></div><div><i>Hf -0.000000000 -0.000000000 -0.000000000</i></div><div><i>S 0.666666667 0.333333333 0.257234636</i></div><div><i>S 0.333333333 0.666666667 -0.257234636</i></div><div><i> K_POINTS automatic</i></div><div><i>10 8 8 0 0 0</i></div><div style="font-weight:bold"><br></div></div><div style="font-weight:bold">The final equilibrium lattice structure obtained by cp.x is:</div><div><div><b> </b><i> CELL_PARAMETERS</i></div><div><i> 8.27944202 -3.49986616 -1.28541441</i></div><div><i> 0.43381045 6.25063702 -0.26433640</i></div><div><i> -1.81611680 -0.30736678 9.28229385</i></div><div><i><br></i></div><div><i> System Density [g/cm^3] : 3.7550323993</i></div><div><i><br></i></div><div><i><br></i></div><div><i> System Volume [A.U.^3] : 477.6950599279</i></div><div><i><br></i></div><div><i><br></i></div><div><i> Center of mass square displacement (a.u.): 0.271737</i></div><div><i><br></i></div><div><i> Total stress (GPa)</i></div><div><i> -0.00003957 0.00000336 0.00017132</i></div><div><i> 0.00000336 -0.00001393 0.00003875</i></div><div><i> 0.00017132 0.00003875 0.00048005</i></div><div><i> ATOMIC_POSITIONS</i></div><div><i> Hf -0.57392945538368E+00 -0.32523714658422E+00 -0.78842946683202E-01</i></div><div><i> S 0.61817237992192E+01 0.34715217744206E+01 0.20852180260292E+00</i></div><div><i> S 0.31507619982481E+00 0.41860506478142E+01 -0.20961035507250E+01</i></div><div><i><br></i></div><div><i> ATOMIC_VELOCITIES</i></div><div><i> Hf -0.49417894612947E-07 -0.41246570825668E-07 -0.28182774835127E-06</i></div><div><i> S 0.29443574450584E-06 0.17988901894696E-06 0.34817154465079E-06</i></div><div><i> S -0.14657506118618E-06 -0.56477323752712E-07 0.49507043808484E-06</i></div><div><i><br></i></div><div><i> Forces acting on atoms (au):</i></div><div><i> Hf -0.18727766763523E-03 -0.15291863668542E-03 -0.99976280595181E-03</i></div><div><i> S 0.33856074345196E-03 0.20689440901408E-03 0.40153992932368E-03</i></div><div><i> S -0.17602213243772E-03 -0.68887225779463E-04 0.57298561574671E-03</i></div><div><i><br></i></div><div>A visualization is attached here </div><div style="font-weight:bold">
<img src="cid:ii_jflvrr3t1_162938e849a1b032" width="438" height="430" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 700; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;">
<br><br></div></div><div style="font-weight:bold">while by pwscf, the equilibrium lattice structure is:</div><div><div><i> CELL_PARAMETERS</i></div><div><i> 6.90298059 -3.45149030 0.00000000</i></div><div><i> 0.00000000 5.97815655 0.00000000</i></div><div><i> 0.00000000 0.00000000 10.68526745</i></div><div><i><br></i></div><div><i> System Density [g/cm^3] : 4.0679453101</i></div><div><i><br></i></div><div><i><br></i></div><div><i> System Volume [A.U.^3] : 440.9499858676</i></div><div><i><br></i></div><div><i><br></i></div><div><i> Center of mass square displacement (a.u.): 0.000000</i></div><div><i><br></i></div><div><i> Total stress (GPa)</i></div><div><i> 32.06481501 -0.01335027 -0.00956254</i></div><div><i> -0.01335027 32.07951164 -0.00592770</i></div><div><i> -0.00956139 -0.00592704 2.04176052</i></div><div><i> ATOMIC_POSITIONS</i></div><div><i> Hf 0.00000000000000E+00 -0.00000000000000E+00 -0.00000000000000E+00</i></div><div><i> S 0.34514902988605E+01 0.19927188491672E+01 0.27486208819801E+01</i></div><div><i> S -0.34514902047533E-08 0.39854377043125E+01 -0.27486208819801E+01</i></div><div><i><br></i></div><div><i> ATOMIC_VELOCITIES</i></div><div><i> Hf 0.00000000000000E+00 0.00000000000000E+00 0.00000000000000E+00</i></div><div><i> S 0.00000000000000E+00 0.00000000000000E+00 0.00000000000000E+00</i></div><div><i> S 0.00000000000000E+00 0.00000000000000E+00 0.00000000000000E+00</i></div><div><i><br></i></div><div><i> Forces acting on atoms (au):</i></div><div><i> Hf 0.70847502228925E-03 0.43071957102166E-03 -0.17703368862259E-04</i></div><div><i> S -0.52668423530029E-03 -0.28607208606422E-03 -0.81547327015321E-01</i></div><div><i> S -0.41998284595312E-03 -0.22039679837681E-03 0.81837284893753E-01</i></div><div style="font-weight:bold"><br></div></div><div style="">A visulization is attached below</div><div style="">
<img src="cid:ii_jflvqr3y0_162938dccb675c27" width="475" height="421" style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: small; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 700; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; background-color: rgb(255, 255, 255); text-decoration-style: initial; text-decoration-color: initial;">
<br></div><div style="font-weight:bold"><br></div><div style="font-weight:bold"><br></div><div style="">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. </div><div style=""><br></div><div style="">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?</div><div style=""><br></div><div style="">Thank you in advance for your help, sincerely!<br><br></div><div style="">Best</div><div style="">Jie</div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div style="font-size:12.8px">------------------------------------------------------------------------------------------------------------------------<br>Jie Peng</div><div style="font-size:12.8px">PhD student<br>2134 Glenn Martin Hall, Mechanical Engineering, University of Maryland<br>College Park, Maryland, USA<br>Phone:(+1) 240-495-9445<br></div><div style="font-size:12.8px">Email: <a href="mailto:jiepeng@umd.edu" target="_blank">jiepeng@umd.edu</a><br></div></div><div><br></div></div></div>
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