PWSCF users: I have been struggling for quite some time to perform a vc-relax calculation on a simple system of 96 Cu atoms. I am confident that the input is correct as an ion relaxation run converges in one scf cycle to a pressure of -11.54 kbar with the same parameters as the vc-relax calculation (shown below).
As seen in the output file, the problem with the vc-relax calculation is that the SCF error will increase with each iteration. I have tried to remedy this issue by restricting the maximum movement distance of both the cell and ions to no avail. Unfortunately, I cannot turn on symmetry as I am using this as a test case for further calculations of Al-Cu solid solutions. Is there anything terribly wrong with my input? Should I impose symmetry despite the addition of Al to the Cu lattice? Thanks for your help. -------------- next part -------------- A non-text attachment was scrubbed... Name: vc-relax_data.tar.gz Type: application/x-gzip Size: 43126 bytes Desc: not available Url : http://www.democritos.it/pipermail/pw_forum/attachments/20100829/a0690f01/attachment-0001.bin -------------- next part -------------- &CONTROL calculation = 'vc-relax' , restart_mode = ?from_scratch? , wf_collect = .false. , outdir = './' , pseudo_dir = './' , prefix = 'Cu' , forc_conv_thr = 2.0d-2, etot_conv_thr = 1.0d-3, tstress = .true. , verbosity = 'minimal' , disk_io = 'none' , tprnfor = .true. , / &SYSTEM ibrav = 8, celldm(1) = 9.505756, celldm(2) = 1.735408, celldm(3) = 4.921944, nat = 96, ntyp = 1, ecutwfc = 22 , ecutrho = 220 , nosym = .true. , occupations = 'smearing' , degauss = 0.022 , smearing = 'methfessel-paxton' , / &ELECTRONS conv_thr = 1.0d-5 , mixing_beta = 0.7 , / &IONS ion_dynamics = 'bfgs' , / &CELL press = 0.0 , press_conv_thr = 5.0d0, cell_dofree = 'xyz' , cell_dynamics = 'bfgs' , / ATOMIC_SPECIES Cu 63.54600 Cu.pw91-n-van_ak.UPF ATOMIC_POSITIONS (crystal) Cu 0.000000000 -0.000082163 -0.000018624 ... K_POINTS automatic 6 4 2 1 1 1 1 =================================================================== Christopher J. O'Brien cjobrien at ncsu.edu https://sites.google.com/a/ncsu.edu/cjobrien/ See what I'm citing at http://www.citeulike.org/cjo123 Ph.D. Candidate Computational Materials Group Department of Materials Science & Engineering North Carolina State University __________________________________________________________________ Please send all documents in PDF, HTML, RTF, DVI, PS or plain text. For Word documents: Please use the 'Save as PDF' option before sending. ===================================================================
