<div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial"><div style="line-height:1.7;color:#000000;font-size:14px;font-family:Arial"><div>Dear all,</div><div>I want to calculate the Raman tensor. I First do a scf calculation (pw.x), followed by PHonon calculation (ph.x), and I got the following message:</div><br><div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div><div> Error in routine cdiaghg (5):</div><div> S matrix not positive definite</div><div> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%</div><div><br></div><div>Input file for pw.x is</div><div><div><span style="color: rgb(136, 0, 0);">&CONTROL</span></div><div><span style="color: rgb(136, 0, 0);"> title = scf,</span></div><div><span style="color: rgb(136, 0, 0);"> prefix = 'graphene'</span></div><div><span style="color: rgb(136, 0, 0);"> calculation = 'scf' ,</span></div><div><span style="color: rgb(136, 0, 0);"> restart_mode = 'from_scratch' ,</span></div><div><span style="color: rgb(136, 0, 0);"> wf_collect = .false. ,</span></div><div><span style="color: rgb(136, 0, 0);"> outdir = './' ,</span></div><div><span style="color: rgb(136, 0, 0);"> pseudo_dir = '~/ppqe' ,</span></div><div><span style="color: rgb(136, 0, 0);"> etot_conv_thr = 1.0d-5 ,</span></div><div><span style="color: rgb(136, 0, 0);"> forc_conv_thr = 1.0d-4 ,</span></div><div><span style="color: rgb(136, 0, 0);"> tstress = .true. ,</span></div><div><span style="color: rgb(136, 0, 0);"> tprnfor = .true. ,</span></div><div><span style="color: rgb(136, 0, 0);"> nstep = 100 ,</span></div><div><span style="color: rgb(136, 0, 0);">/</span></div><div><span style="color: rgb(136, 0, 0);">&SYSTEM</span></div><div><span style="color: rgb(136, 0, 0);"> ibrav = 4,</span></div><div><span style="color: rgb(136, 0, 0);"> celldm(1) = 4.5961617417745675,</span></div><div><span style="color: rgb(136, 0, 0);"> celldm(3) = 10,</span></div><div><span style="color: rgb(136, 0, 0);"> nat = 2,</span></div><div><span style="color: rgb(136, 0, 0);"> ntyp = 1,</span></div><div><span style="color: rgb(136, 0, 0);"> ecutwfc = 80,</span></div><div><span style="color: rgb(136, 0, 0);"> nosym = .false. ,</span></div><div><span style="color: rgb(136, 0, 0);">/</span></div><div><span style="color: rgb(136, 0, 0);">&ELECTRONS</span></div><div><span style="color: rgb(136, 0, 0);"> electron_maxstep = 100,</span></div><div><span style="color: rgb(136, 0, 0);"> conv_thr = 1.D-12,</span></div><div><span style="color: rgb(136, 0, 0);"> mixing_beta = 0.3</span></div><div><span style="color: rgb(136, 0, 0);">/</span></div><div><span style="color: rgb(136, 0, 0);">ATOMIC_SPECIES</span></div><div><span style="color: rgb(136, 0, 0);"> C 14.0067 C.pz-hgh.UPF</span></div><div><span style="color: rgb(136, 0, 0);">ATOMIC_POSITIONS crystal</span></div><div><span style="color: rgb(136, 0, 0);">C 0.0 0.0 0.0</span></div><div><span style="color: rgb(136, 0, 0);">C 1/3 -1/3 0.0</span></div><div><span style="color: rgb(136, 0, 0);">K_POINTS automatic</span></div><div><span style="color: rgb(136, 0, 0);"> 16 16 1 0 0 0</span></div></div><div><br></div><div>The input file for ph.x is</div><div><div><span style="color: rgb(136, 0, 0);">phonon</span></div><div><span style="color: rgb(136, 0, 0);">&inputph</span></div><div><span style="color: rgb(136, 0, 0);"> tr2_ph=1.0d-14,</span></div><div><span style="color: rgb(136, 0, 0);"> prefix='graphene',</span></div><div><span style="color: rgb(136, 0, 0);"> epsil=.true.,</span></div><div><span style="color: rgb(136, 0, 0);"> trans=.true.,</span></div><div><span style="color: rgb(136, 0, 0);"> lraman=.true.,</span></div><div><span style="color: rgb(136, 0, 0);"> amass(1)=12.0,</span></div><div><span style="color: rgb(136, 0, 0);"> outdir='./',</span></div><div><span style="color: rgb(136, 0, 0);"> fildyn='graphene_ir.dynG',</span></div><div><span style="color: rgb(136, 0, 0);"> fildrho='graphene_ir.drho',</span></div><div><span style="color: rgb(136, 0, 0);">/</span></div><div><span style="color: rgb(136, 0, 0);">0.0 0.0 0.0</span></div></div><div><br></div><div>I have tried to calculate the Raman tensor of ZnS with the same procedure, and every thing goes well. But when I use similar input files for graphene, it failed.</div><div><br></div><div>Graphene is a 2-dimensional system, while ZnS is a 3-dimensional crystal. I don't know if this difference is responsible for this failure, since, for 2D system, I have to insert a large vacuum, which is a potential source of problem.</div><div><br></div><div>Thanks in advance!</div><div><br></div><div><br></div><div><br></div><br><div style="position:relative;zoom:1">--<br><div>
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<p>Sincerely Yours</p>
<p>Jason Lee(Àî½ÜÉ)</p>
<p>----------------------------------------------------<br>Jason Lee<br>Ph.D in Physics; President of Sanda Association; Doctoral Student Union<br>School of Physics and Engineering<br>Sun Yat-sen University, 135#Xingang Xi Rd.<br>Guangzhou, 510275, China<br>Tel£º020-84111107(office) Cell: 13560161944(661944)<br><br><br></p>
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