Hello Ramesh, Norm-conserving (NC) pseudopotentials (PP) require higher energy cutoffs. You need NC PP for electron-phonon calculations. NC PP from PseudoDojo website are very good, at least for what I've tested on organic materials. Then you don't need ecutrho for NC PP, which are made to work with default ecutrho = 4 x ecutwfc.
So, you should try first to increase your cutoff, up to 200 Ry should do the job to have the asymptotic behavior with PseudoDojo NC PP (unfortunately, other NC PP may require much higher cutoffs to get the asymptotic behavior). Then you can choose the cutoff where the asymptotic error is just below 1 meV/atom. After you do a vc-relax simulation, always check the verification step at the end of the output. If the pressure tensor is different from the pressure tensor of the last optimization step, then it means your cutoff is not large enough, or your system has converging issues (initial geometry, k-points...). I think your forc_conv_thr of 1e-4 is good. You can tighten a little bit etot_conv_thr to 1e-5 and press_conv_thr to 0.1 kbar. Regards, Xavier ________________________________ From: users <[email protected]> on behalf of Ramesh Kumar Kamadurai via users <[email protected]> Sent: Thursday, October 27, 2022 3:23 AM To: [email protected] <[email protected]> Subject: [QE-users] Electron Phonon Calculation: tolerance limit for P Dear users I am trying to calculate el-Ph coupling constant and other properties for a superconductor. The input file is attached. I am a bit stuck with VC-Relax calculation as the system is not able to stabilize at 0.0 kbar. I followed all the suggestions given in forum 1. Increased Cut-off to maximum 2. Tried USPP,NC, Mixed and currently running with PBE-Sol 3. Sequentially done 2 VC Relax calculation but i am not able to sort out the issue. &CONTROL calculation = "vc-relax" etot_conv_thr = 4.00000e-05 forc_conv_thr = 1.00000e-04 max_seconds = 1.72800e+05 nstep = 100 outdir = "/home/sjacobs/tmp/" prefix = "PDZ-VCRELAX" pseudo_dir = "C:\Users\RAMESH\.burai\.pseudopot" tprnfor = .TRUE. tstress = .TRUE. verbosity = "high" / &SYSTEM a = 6.36512e+00 degauss = 7.34986e-03 ecutrho = 6.40000e+02 ecutwfc = 8.00000e+01 ibrav = 2 nat = 4 nosym = .FALSE. nspin = 1 ntyp = 3 occupations = "smearing" smearing = "marzari-vanderbilt" / &ELECTRONS conv_thr = 8.00000e-10 electron_maxstep = 80 mixing_beta = 4.00000e-01 startingpot = "atomic" startingwfc = "atomic+random" / &IONS ion_dynamics = "bfgs" / &CELL cell_dofree = "all" cell_dynamics = "bfgs" press = 0.00000e+00 press_conv_thr = 5.00000e-01 / K_POINTS {automatic} 12 12 12 0 0 0 ATOMIC_SPECIES Ga 69.72300 Ga.pbesol-dnl-rrkjus_psl.1.0.0.UPF Pd 106.42000 Pd_ONCV_PBEsol-1.0.upf Zr 91.22400 zr_pbesol_v1.uspp.F.UPF ATOMIC_POSITIONS {crystal} Zr 0.000000 0.000000 0.000000 Ga 0.493162 0.493162 0.493162 Pd 0.739743 0.739743 0.739743 Pd 0.246581 0.246581 0.246581 The output stress is given below entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= 2.67 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.41 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.82 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= 0.56 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= 0.13 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.08 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.23 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.35 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.50 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.63 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.77 entering subroutine stress ... total stress (Ry/bohr**3) (kbar) P= -0.83 My question is What is the optimal pressure value to avoid negative frequencies for electron phonon calculation ? Is there any mistake in my input file ? Thanks in advance Regards Ramesh Asst. Professor GITAM University Vizag, India
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