Hi,<br><br> The total energy doesn't converge till 80 Ryd of ecutwfc. I am using Ni and Ti USPPs (Ti.pbe-sp-van_ak.UPF, Ni.pbe-nd-rrkjus.UPF). My calculations become very slow while using such a large kinetic energy cutoff. am I doing something wrong here?<br>
<br>regards,<br>Karthik<br><br><div class="gmail_quote">On Tue, Aug 17, 2010 at 4:46 PM, Stefano de Gironcoli <span dir="ltr"><<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
please note that the two outputs that you submitted ARE NOT examples of<br>
vc-relaxation but of structural relaxation of the internal coordinates<br>
only. Your question is anyway legittimate...<br>
Are you sure to have converged the total energy of your system with<br>
respect to cutoff to a sufficient level ?<br>
when comparing different volumes one is using different basis sets in<br>
the two cases. If convergence w.r.t. cutoff is not sufficient this can<br>
lead to sudden decreases of the energy when increasing the volume.<br>
<br>
stefano<br>
SISSA and DEMOCRITOS<br>
<div><div></div><div class="h5"><br>
Guda Karthik wrote:<br>
> Hi,<br>
><br>
> Here are the input and output files.<br>
><br>
> b19_Acklatpos_new.* - original structure<br>
><br>
> b19_pwscf.* - scf calculation with a structure obtained after vc-relax<br>
><br>
> Please have a look if they are of help.<br>
><br>
> regards,<br>
> Karthik<br>
><br>
> On Sat, Aug 14, 2010 at 6:27 AM, Paolo Giannozzi <<a href="mailto:giannozz@democritos.it">giannozz@democritos.it</a>>wrote:<br>
><br>
><br>
>> On Aug 4, 2010, at 4:41 , Guda Karthik wrote:<br>
>><br>
>><br>
>>> I am trying to relax an orthorhombic structure using vc-relax<br>
>>> (celldofree - xyz). I start with a structure which is at a Pressure<br>
>>> of -20.5 Kbar and at the end of the vc-relax I get a structure<br>
>>> which is at a pressure of -0.21 Kbar. Surprisingly, the structure<br>
>>> at pressure closer to zero is higher in energy than the original<br>
>>> structure by 8 * 10^-4 eV/formula unit. All the symmetry elements<br>
>>> have been conserved during relaxation and the initial and final<br>
>>> structures are the same. I am not able to make sense of this<br>
>>> result. I observe this inconsistency in my B2 structure as well.<br>
>>> Please help regarding this.<br>
>>><br>
>> hard to help without input and output<br>
>><br>
>> P.<br>
>> ---<br>
>> Paolo Giannozzi, Dept of Physics, University of Udine<br>
>> via delle Scienze 208, 33100 Udine, Italy<br>
>> Phone +39-0432-558216, fax +39-0432-558222<br>
>><br>
>><br>
>><br>
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</div></div></blockquote></div><br><br clear="all"><br>-- <br>Karthik Guda<br>Graduate Student<br>Materials Engineering<br>Purdue University<br><br>