<div dir="ltr"><div><div><div><div>Ok,<br></div>My question concerns your comment that "One should use instead<br>
CELL_PARAMETERS (angstrom)<br>
to specify lattice vectors in A" where as what I obtain in vc-relax output is <br>CELL_PARAMETERS (alat= 8.11400000).<br></div>So, I am wondering if there is a particular way I ought to define my celldm(1) or any other parameter in other to obtain output in the format CELL_PARAMETERS (angstrom).<br><br></div>Thanks a lot for your help,<br></div>Isaiah<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Fri, Jun 23, 2017 at 11:16 AM, Paolo Giannozzi <span dir="ltr"><<a href="mailto:p.giannozzi@gmail.com" target="_blank">p.giannozzi@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I don't remember what the code prints during a vc-relax calculation,<br>
but I know for sure that the output of ATOMIC_POSITIONS and<br>
CELL_PARAMETERS is in a format that can be used as input.<br>
<div class="HOEnZb"><div class="h5"><br>
On Fri, Jun 23, 2017 at 8:30 AM, Isaiah Moses <<a href="mailto:imoses87@gmail.com">imoses87@gmail.com</a>> wrote:<br>
> Hi Paolo,<br>
> But how does one set CELL_PARAMETERS (angstrom)?<br>
> Because I observe that the output I obtain from vc-relax is automatically<br>
> set to<br>
> CELL_PARAMETERS (alat= 8.11400000).<br>
> Does that has to do with the unit of celldm?<br>
><br>
> I must be missing something on theses units' usage.<br>
><br>
> I appreciate your usual prompt response,<br>
> Isaiah<br>
><br>
> On Fri, Jun 23, 2017 at 7:16 AM, Paolo Giannozzi <<a href="mailto:p.giannozzi@gmail.com">p.giannozzi@gmail.com</a>><br>
> wrote:<br>
>><br>
>> And, by the way, it is a bad habit to set the lattice parameter to the<br>
>> conversion factor between a.u. and A. One should use instead<br>
>> CELL_PARAMETERS (angstrom)<br>
>> to specify lattice vectors in A<br>
>><br>
>> Paolo<br>
>><br>
>> On Fri, Jun 23, 2017 at 4:55 AM, Stefano de Gironcoli <<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>><br>
>> wrote:<br>
>> > The lattice parameter does not change, it is not updated along vc-relax,<br>
>> > the<br>
>> > lattice vectors do.<br>
>> > Using bfgs you don't need to define dt<br>
>> ><br>
>> > stefano<br>
>> > (sent from my phone)<br>
>> ><br>
>> > On 23 Jun 2017, at 01:55, Brendan Smith <<a href="mailto:mrbsmith58@gmail.com">mrbsmith58@gmail.com</a>> wrote:<br>
>> ><br>
>> > Hello all,<br>
>> ><br>
>> > I am doing a the following vc-relax calculation and the unit cell<br>
>> > paramters<br>
>> > are not changing. I have looked at other posts which descirbes similar<br>
>> > problems, but it does not remedy my problem. Below is my input.<br>
>> > Best,<br>
>> > Brendan<br>
>> ><br>
>> ><br>
>> > &CONTROL<br>
>> > calculation = 'vc-relax',<br>
>> > dt = 20.67055,<br>
>> > nstep = 1000,<br>
>> > pseudo_dir = './'<br>
>> > outdir = './',<br>
>> > prefix = 'x',<br>
>> > disk_io = 'low',<br>
>> > /<br>
>> ><br>
>> > &SYSTEM<br>
>> > ibrav = 0,<br>
>> > celldm(1) = 1.89,<br>
>> > nat = 16,<br>
>> > ntyp = 3,<br>
>> > nspin = 1,<br>
>> > nbnd = 120,<br>
>> > ecutwfc = 70,<br>
>> > ecutrho = 560,<br>
>> > tot_charge = 0.0,<br>
>> > occupations = 'smearing',<br>
>> > smearing = 'gaussian',<br>
>> > degauss = 0.005,<br>
>> > nosym = .true.,<br>
>> > /<br>
>> ><br>
>> > &ELECTRONS<br>
>> > electron_maxstep = 1000,<br>
>> > conv_thr = 1.D-5,<br>
>> > mixing_beta = 0.45,<br>
>> > /<br>
>> ><br>
>> > &IONS<br>
>> > ion_dynamics = 'bfgs',<br>
>> > ion_temperature = 'andersen',<br>
>> > tempw = 300.00 ,<br>
>> > nraise = 1,<br>
>> > /<br>
>> ><br>
>> > &CELL<br>
>> > cell_dynamics = 'bfgs',<br>
>> > press_conv_thr = 0.5,<br>
>> > cell_factor = 2.0,<br>
>> > cell_dofree = 'all',<br>
>> > /<br>
>> ><br>
>> > ATOMIC_SPECIES<br>
>> > O 15.9994 O_pbe_v1.2.uspp.F.UPF<br>
>> > V 50.9415 V_pbe_v1.uspp.F.UPF<br>
>> > Pb 207.2 Pb.pbe-dn-rrkjus_psl.0.2.2.UPF<br>
>> ><br>
>> > K_POINTS automatic<br>
>> > 3 3 3 0 0 0<br>
>> ><br>
>> > CELL_PARAMETERS (alat)<br>
>> > 11.5439996719 0.0000000000 0.0000000000<br>
>> > 0.0000000000 3.5710000992 0.0000000000<br>
>> > 0.0000000000 0.0000000000 4.3829998970<br>
>> ><br>
>> > ATOMIC_POSITIONS (alat)<br>
>> > V 6.940599 0.892750 0.475994<br>
>> > V 4.603400 2.678250 3.907006<br>
>> > V 10.375401 0.892750 0.475994<br>
>> > V 1.168599 2.678250 3.907006<br>
>> > O 4.974309 0.892750 4.370728<br>
>> > O 6.569691 2.678250 0.012272<br>
>> > O 0.797690 0.892750 4.370728<br>
>> > O 10.746309 2.678250 0.012272<br>
>> > O 6.978348 0.892750 2.058695<br>
>> > O 4.565652 2.678250 2.324305<br>
>> > O 10.337652 0.892750 2.058695<br>
>> > O 1.206349 2.678250 2.324305<br>
>> > O 8.658000 0.892750 0.003506<br>
>> > O 2.886000 2.678250 4.379493<br>
>> > Pb 8.500000 2.500000 1.500000<br>
>> > Pb 3.000000 1.500000 3.000000<br>
>> ><br>
>> ><br>
>> ><br>
>> ><br>
>> > ______________________________<wbr>_________________<br>
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>><br>
>><br>
>><br>
>> --<br>
>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
>> Phone +39-0432-558216, fax +39-0432-558222<br>
>> ______________________________<wbr>_________________<br>
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><br>
><br>
><br>
><br>
> --<br>
> Isaiah Abu Moses<br>
> Graduate Student,<br>
> Physics Department,<br>
> University of Ibadan,<br>
> Nigeria<br>
><br>
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> Pw_forum mailing list<br>
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<br>
<br>
<br>
--<br>
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,<br>
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy<br>
Phone +39-0432-558216, fax +39-0432-558222<br>
______________________________<wbr>_________________<br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div><div>Isaiah Abu Moses<br></div><div>Graduate Student,<br></div>Physics Department,<br></div>University of Ibadan,<br></div>Nigeria<br></div></div></div></div></div></div>
</div>