<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Does vc-relax change also celldm(3)?</div><div><br></div><div>BTW, 0.06 for degauss is a tad too large.</div><div><br></div><div>Nicola<br><br>Sent from a tiny keyboard...</div><div><br>On 18 May 2013, at 22:15, Dongsheng Zhang <<a href="mailto:zhdsheng21@gmail.com">zhdsheng21@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><div dir="ltr"><div><div><div>Hi,<br><br>I have used vc-relax to get the optimum lattice constant for Ti HCP crystal. The result is very close to the experiment data. However, when I tried to calc the total energy at different lattice constant to get the dependency of total energy on the lattice constant, I got the different answer to the optimum lattice constant. Could anyone tell me what's wrong in my simulations? Thanks.<br>
<br></div><div>Dongsheng<br></div><div><br></div>The input for vc-relax method:<br><br><br> &control<br> prefix='ti',<br> pseudo_dir = '/home1/01993/zhdsheng/espresso/pseudo/',<br> outdir='/scratch/01993/zhdsheng/Ti_K6L6.0/',<br>
calculation='vc-relax',<br> restart_mode='from_scratch'<br> /<br> &system <br> ibrav= 4, celldm(1) =6.0,celldm(3) =1.633, nat= 2, ntyp= 1,<br> occupations='smearing', smearing='marzari-vanderbilt', degauss=0.06,<br>
ecutwfc =150, <br> <br> /<br> &electrons<br> /<br> &ions <br> /<br> &cell<br> cell_dynamics='bfgs' <br> /<br>ATOMIC_SPECIES<br> Ti 47.867 Ti.pbe-mt_fhi.UPF<br>ATOMIC_POSITIONS<br> Ti 0.000000000000 0.000000000000 0.000000000000<br>
Ti 0.666666666666 0.333333333333 0.50000000000<br>K_POINTS automatic<br> 6 6 6 1 1 1 <br><br></div><div>The optimum lattice constant from this input file is 5.576<br><br></div>The input for manual optimization:<br>
</div>
<a href="http://template.in">template.in</a>:<br><br>&control<br> prefix='ti',<br> pseudo_dir = '/home1/01993/zhdsheng/espresso/pseudo/',<br> outdir='/scratch/01993/zhdsheng/Ti_try/',<br>
restart_mode='from_scratch'<br> /<br> &system <br> ibrav= 4, celldm(1) =alat,celldm(3) =1.633, nat= 2, ntyp= 1,<br> occupations='smearing', smearing='marzari-vanderbilt', degauss=0.06,<br>
ecutwfc =150, <br> <br> /<br> &electrons<br> /<br> &ions <br> /<br>ATOMIC_SPECIES<br> Ti 47.867 Ti.pbe-mt_fhi.UPF<br>ATOMIC_POSITIONS<br> Ti 0.000000000000 0.000000000000 0.000000000000<br> Ti 0.666666666666 0.333333333333 0.50000000000<br>
K_POINTS automatic<br> 6 6 6 1 1 1 <br><br><div>alat is the lattice variable. The result from this input file is:<br><br></div><div>alat etotal<br></div><div>5.0760 -13.57602170<br>5.1760 -13.61996733<br>5.2760 -13.65721285<br>
5.3760 -13.68841125<br>5.4760 -13.71412487<br>5.5760 -13.73484556<br>5.6760 -13.75101618<br>5.7760 -13.76303624<br>5.8760 -13.77128114<br>5.9760 -13.77609614<br>6.0760 -13.77784664<br>6.1760 -13.77685770<br>6.2760 -13.77353840<br>
6.3760 -13.76853094<br>6.4760 -13.76290015<br>6.5760 -13.75652953<br>6.6760 -13.74869787<br>6.7760 -13.74207406<br><br><br></div></div>
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