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<p><tt>Dear </tt>Jie Peng,</p>
<p> 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.</p>
<p> I think this is the most relevant difference in your two
inputs.</p>
<p> To see if this is the case you can repeat the pw.x calculation
with <br>
</p>
<p>K_POINT Gamma<br>
</p>
<p> Is the 10 8 8 grid really necessary ? is the system metallic ?
<br>
</p>
<p> 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.<br>
</p>
<p>stefano<br>
</p>
<br>
<div class="moz-cite-prefix">On 05/04/2018 04:16, Jie Peng wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAJTOooHJnC0XmgG4pGoMk0kop7DtG-48v7487xq2wWVhDpoi_A@mail.gmail.com">
<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:part1.C12A770C.5B57FD7A@sissa.it"
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;" class="" width="438" height="430">
<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:part2.BDAE1642.F544B821@sissa.it"
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;
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<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>
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<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>
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<div style="">Thank you in advance for your help, sincerely!<br>
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<div style="">Best</div>
<div style="">Jie</div>
-- <br>
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<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>
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<div style="font-size:12.8px">Email: <a
href="mailto:jiepeng@umd.edu" target="_blank"
moz-do-not-send="true">jiepeng@umd.edu</a><br>
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