<div>Dear all,<br> In the namelist of control, it seems that CP code can do a lot of calculations(scf, nscf,relax,vc-relax,vc-cp,...). I have tested the example18, which shows how to use cp.x to perform molecular dynamics simulation of SiO2. The first step is to get the ground state of the electronic system. I think there should be a previous step to get the equilibrium structure of SiO2. However I find there isn't any examples to do vc-relax using CP code. If I want to CP code to do vc-relax calculation, how to set corresponding parameters? In PW code, the vc-relax calculation is done in temperature=0 K condition which ignore the kinetic energy of ions. But in CP code, the vc-relax calculation complains that the temperature can not be 0 K. So I set the temperatures of ions and cell are 'not_controlled'. In the 'not_controlled' calculation, the cell of the system expands with the increasing steps. It is strange. How to do vc-relax in CP code? The following is the input file and some information from output file.</div>
<div>input</div>
<div> &control<br> calculation='vc-relax',<br> restart_mode='from_scratch',<br> nstep=100, <br> iprint=1, <br> isave=1,<br> dt=8.0,<br> ndr=91, <br> ndw=92,<br> pseudo_dir='./',<br>
outdir='./',<br> /<br> &system<br> ibrav=8, <br> celldm(1)=9.28990, <br> celldm(2)=1.73206,<br> celldm(3)=1.09955,<br> nat=18,<br> ntyp=2, <br> nbnd=48, <br> nelec=96, <br> nspin=1,<br>
ecutwfc=20.0, <br> ecutrho=150.0,<br> nr1b=16, <br> nr2b=16, <br> nr3b=16,<br> qcutz=150., <br> q2sigma=2.0, <br> ecfixed=16.0,<br> /<br> &electrons<br> electron_dynamics='verlet', <br>
ortho_max=100,<br> emass=700., <br> emass_cutoff=3.,<br> /<br> &ions<br> ion_dynamics='verlet', <br> ion_radius(1)=1.0, <br> ion_radius(2)=1.0,<br> /<br> &cell<br> cell_dynamics='pr', <br>
press=0.D0<br> /<br>ATOMIC_SPECIES<br> O 16.00 O.pz-rrkjus.UPF<br> Si 28.00 Si.vbc.UPF<br>ATOMIC_POSITIONS<br> O 3.18829368 14.83237039 1.22882961<br> O 7.83231469 6.78704039 1.22882961<br> O 2.07443467 5.99537992 4.73758250<br>
O 6.72031366 14.04231898 4.73758250<br> O 3.96307134 11.26989826 7.87860582<br> O 8.60802134 3.22295920 7.87860582<br> O 3.96307134 4.81915267 9.14625133<br> O 8.60802134 12.86448267 9.14625133<br> O 3.18736469 1.25668055 5.58029607<br>
O 7.83324368 9.30201055 5.58029607<br> O 2.07536366 10.09206195 2.07358613<br> O 6.71938467 2.04673195 2.07358613<br>Si 0.28891589 8.04533000 3.40456284<br>Si 4.93386589 0.00000000 3.40456284<br>Si 2.13389003 12.27717358 -0.04188031<br>
Si 6.77884003 4.23184358 -0.04188031<br>Si 2.13389003 3.81348642 6.85202747<br>Si 6.77884003 11.85881642 6.85202747<br></div>
<div> </div>
<div>some information form output file</div>
<div>step 1</div>
<div> CELL_PARAMETERS<br> 9.28990000 0.00000000 0.00000000<br> 0.00000000 16.09066419 0.00000000<br> 0.00000000 0.00000000 10.21470954</div>
<div> </div>
<div> Total stress (GPa)<br> 1582.97951906 -1.16929980 -21.68011687<br> -1.17872209 1618.59651136 11.14345397<br> -21.82861949 11.00777251 1647.98672617</div>
<div> </div>
<div> </div>
<div>step 50</div>
<div> CELL_PARAMETERS<br> 16.77885645 -0.00946391 0.01423662<br> -0.01456595 21.79804238 -0.00448412<br> 0.01470088 -0.00304592 17.53521234</div>
<div> Total stress (GPa)<br> -11.78865891 0.58606252 1.97796694<br> 0.58606252 95.04276174 -4.47537576<br> 1.97796694 -4.47537576 7.30569481</div>
<div> </div>
<div>step 100</div>
<div> CELL_PARAMETERS<br> 26.25499658 -0.05592615 0.05092035<br> -0.07610163 31.84643730 0.00083894<br> 0.05276954 0.00223134 27.45646153</div>
<div> Total stress (GPa)<br> -21.80901098 0.11600975 -0.06986058<br> 0.11600975 -1.12040472 0.25103238<br> -0.06986058 0.25103238 -19.41116556</div>
<div>-- <br>Y. C. Cheng<br>Department of Physics<br>Nanjing University<br>Nanjing 210093<br>P. R. China<br>Tel: 86-25-83592907<br>Email: <a href="mailto:yccheng.nju@gmail.com">yccheng.nju@gmail.com</a><br></div>