Dear Marcos Please, see this link, it is explanatory for vc-relax :
http://qe-forge.org/pipermail/pw_forum/2014-March/103393.html Best regards, Nucu On Fri, June 6, 2014 7:21 am, Marcos Ver??ssimo Alves wrote: > Thanks, Arles, but I opened the relaxation on xcrysden and on the first > step the cell was hexagonal. > > Best, > > Marcos > > On Thursday, June 5, 2014, Arles V. Gil Rebaza <arvifis at gmail.com> wrote: > >> Dear Marcos, please review your CELL_PARAMETERS tag..!! I thing that >> there >> are some mistakes... you are using a square 2D lattice and not a >> hexagonal >> one. >> >> Best >> >> PhD. Arles V. Gil Rebaza >> Instituto de F??sica La Plata >> La Plata - Argentina >> >> >> 2014-06-05 21:40 GMT-03:00 Marcos Ver??ssimo Alves < >> marcos.verissimo.alves at gmail.com >> <javascript:_e(%7B%7D,'cvml','marcos.verissimo.alves at gmail.com');>>: >> >>> Hi all, >>> >>> I am trying to perform a cell optimization for graphene in which I >>> would >>> like to fix the atomic positions so as to have arbitrary bond lengths, >>> and >>> see what happens to the in-plane cell vectors. Thus I would like to >>> keep >>> the atomic positions fixed and let the in-plane cell vectors change. >>> >>> I am using vc-relax with cell_dofree="2dxy" and I am (theoretically) >>> fixing atomic positions (specified in Angstrom) with "0 0 0" after the >>> cartesian coordinates. The problem is, the coordinates do not remain >>> fixed >>> during the cell optimization: >>> >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.508583432 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.553137965 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.583982256 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.592677072 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.597484048 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.599092143 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.598936919 0.000000000 7.000000000 0 0 0 >>> -- >>> ATOMIC_POSITIONS (angstrom) >>> C 0.000000000 0.000000000 7.000000000 0 0 0 >>> C 1.598936919 0.000000000 7.000000000 0 0 0 >>> >>> My input is as follows: >>> >>> &control >>> calculation='vc-relax' >>> restart_mode='from_scratch', >>> prefix='graphene', >>> pseudo_dir = '/home/mverissi/pseudos_espresso', >>> outdir='./' >>> / >>> &system >>> ibrav=0, >>> celldm(1)=4.073139044, >>> nat=2, >>> ntyp=1, >>> nspin = 1, >>> ecutwfc = 28.0, >>> ecutrho = 252.0, >>> occupations='smearing', >>> smearing='methfessel-paxton', >>> degauss=0.001, >>> nbnd=10, >>> / >>> &electrons >>> conv_thr = 1.0e-9, >>> mixing_beta = 0.7 >>> / >>> &ions >>> ion_dynamics='bfgs' >>> / >>> &cell >>> cell_dynamics = 'bfgs', >>> cell_dofree = '2Dxy', >>> / >>> ATOMIC_SPECIES >>> C 12.0107 C.pbe-rrkjus.UPF >>> ATOMIC_POSITIONS {angstrom} >>> C 0.0 0.0 7.0 0 0 0 >>> C 1.42 0.0 7.0 0 0 0 >>> K_POINTS {automatic} >>> 24 24 1 0 0 0 >>> CELL_PARAMETERS {alat} >>> 0.866025404 0.5 0.0 >>> 0.866025404 -0.5 0.0 >>> 0.000000000 0.0 6.0 >>> >>> Am I making some silly mistake here? The version of Espresso in use is >>> 5.0.2. Sorry if this has already come up, but I couldn't find anything >>> similar to my problem. >>> >>> Best regards, >>> >>> Marcos >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> Pw_forum at pwscf.org <javascript:_e(%7B%7D,'cvml','Pw_forum at >>> pwscf.org');> >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >> >> >> >> -- >> ###---------> Arles V. <---------### >> > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://pwscf.org/mailman/listinfo/pw_forum
