<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Gentlemen and ladies, <br><br>I have some rookie questions about VC-relax. I've pasted the input file and greps of Total energy, Total Forces and stresses below. Its the same problem of oscillations that has been posted before. Here are my questions.<br><br>1). how can it be that while the forces and stresses are oscillating the total energy continues to decrease albeit slowly? Am I really relaxing fine but just have a long way to go?<br>2) I've read many posts suggestioning an MD run to determine an effective dt but I don't think I understand. I run molecular dynamics and look for the oscillation period of the total forces???? Then use a dt equal to some fraction of the period?<br>3) I've seen conflicting suggestions
on whether the default cell mass is a good guess. any further thoughts on this?<br>4) I'm starting off with "! no symmetries" and hoping to relax to a point where I find symmetries. is VC-relax even appropriate for this application?<br><br>thanks in advance!<br><br>Tim Mason<br>Graduate student physics<br>University of Missouri St. Louis<br><br>! total energy = -130.99725337 Ry<br>! total energy = -130.99742389 Ry<br>! total energy = -130.99765896 Ry<br>! total energy = -130.99788028
Ry<br>! total energy = -130.99814044 Ry<br>! total energy = -130.99838484 Ry<br>! total energy = -130.99862662 Ry<br>! total energy = -130.99883535 Ry<br>! total energy = -130.99906028 Ry<br>! total energy = -130.99921630 Ry<br>! total energy =
-130.99942817 Ry<br>! total energy = -130.99962083 Ry<br>! total energy = -130.99984032 Ry<br>! total energy = -131.00005894 Ry<br>! total energy = -131.00027167 Ry<br>! total energy = -131.00032697 Ry<br>! total energy = -131.00055195 Ry<br>! total energy
= -131.00075005 Ry<br>! total energy = -131.00092926 Ry<br>! total energy = -131.00110579 Ry<br>! total energy = -131.00128893 Ry<br>! total energy = -131.00152437 Ry<br>! total energy = -131.00176666 Ry<br>! total energy = -131.00201744 Ry<br>! total
energy = -131.00222657 Ry<br><br> Total force = 0.025775 Total SCF correction = 0.000281<br> Total force = 0.020098 Total SCF correction = 0.000361<br> Total force = 0.015661 Total SCF correction = 0.000081<br> Total force = 0.016340 Total SCF correction = 0.000253<br> Total force = 0.012358 Total SCF correction = 0.000853<br> Total force =
0.012918 Total SCF correction = 0.000221<br> Total force = 0.011349 Total SCF correction = 0.000287<br> Total force = 0.013804 Total SCF correction = 0.000249<br> Total force = 0.012754 Total SCF correction = 0.000124<br> Total force = 0.016969 Total SCF correction = 0.000230<br> Total force = 0.011474 Total SCF correction = 0.000262<br> Total force = 0.013177
Total SCF correction = 0.000210<br> Total force = 0.010928 Total SCF correction = 0.000265<br> Total force = 0.009784 Total SCF correction = 0.000097<br> Total force = 0.010154 Total SCF correction = 0.000534<br> Total force = 0.023392 Total SCF correction = 0.000539<br> Total force = 0.018644 Total SCF correction = 0.000303<br> Total force = 0.013266 Total SCF correction
= 0.000284<br> Total force = 0.012565 Total SCF correction = 0.000137<br> Total force = 0.011408 Total SCF correction = 0.000406<br> Total force = 0.013103 Total SCF correction = 0.000212<br> Total force = 0.011107 Total SCF correction = 0.000195<br> Total force = 0.009844 Total SCF correction = 0.000492<br> Total force = 0.010155 Total SCF correction =
0.000692<br> Total force = 0.014920 Total SCF correction = 0.000309<br><br> total stress (Ry/bohr**3) (kbar) P= 0.85<br> total stress (Ry/bohr**3) (kbar) P= 1.09<br> total stress (Ry/bohr**3) (kbar) P=
1.44<br> total stress (Ry/bohr**3) (kbar) P= 2.07<br> total stress (Ry/bohr**3) (kbar) P= 2.36<br> total stress (Ry/bohr**3) (kbar) P= 2.74<br> total stress
(Ry/bohr**3) (kbar) P= 2.96<br> total stress (Ry/bohr**3) (kbar) P= 2.95<br> total stress (Ry/bohr**3) (kbar) P= 2.92<br> total stress (Ry/bohr**3) (kbar)
P= 3.35<br> total stress (Ry/bohr**3) (kbar) P= 3.21<br> total stress (Ry/bohr**3) (kbar) P= 3.13<br> total stress (Ry/bohr**3) (kbar) P= 2.91<br> total stress
(Ry/bohr**3) (kbar) P= 2.85<br> total stress (Ry/bohr**3) (kbar) P= 2.61<br> total stress (Ry/bohr**3) (kbar) P= 1.46<br> total stress (Ry/bohr**3) (kbar)
P= 1.75<br> total stress (Ry/bohr**3) (kbar) P= 2.29<br> total stress (Ry/bohr**3) (kbar) P= 2.03<br> total stress (Ry/bohr**3) (kbar) P= 1.97<br> total stress
(Ry/bohr**3) (kbar) P= 2.01<br> total stress (Ry/bohr**3) (kbar) P= 2.26<br> total stress (Ry/bohr**3) (kbar) P= 2.44<br> total stress (Ry/bohr**3) (kbar)
P= 2.66<br> total stress (Ry/bohr**3) (kbar) P= 2.59<br><br>&CONTROL<br>calculation = "vc-relax",<br>prefix = 'n1',<br>tprnfor = .TRUE.<br>pseudo_dir = '/home/tim/PWSCF/PSPS',<br>outdir='/home/tim/tmp'<br>etot_conv_thr = 1.0D-5,<br>forc_conv_thr = 0.0004,<br>dt = 20<br>nstep = 100<br>/<br><br>&SYSTEM<br>ibrav = 0, nat = 15, ntyp = 5,<br>ecutwfc = 40<br>ecutrho = 480<br>celldm(1) = 1.889725989<br>/<br><br>&ELECTRONS<br>mixing_mode = 'plain',<br>mixing_beta = 0.7,<br>conv_thr = 1.0D-7,<br>/<br><br><br>&IONS<br>ion_dynamics = 'damp',<br>ion_damping = 0.1,<br>ion_positions = 'from_input',<br>pot_extrapolation = "second_order",<br>wfc_extrapolation = "second_order",<br>upscale =
100,<br>/<br><br>&CELL<br>press = 0.0,<br>cell_dynamics = 'damp-w'<br>/<br><br>ATOMIC_SPECIES<br>Li 1.0 Li.pbe-n-van.UPF<br>Ca 1.0 Ca.pbe-nsp-van.UPF<br>N 1.0 N.pbe-rrkjus.UPF<br>H 1.0 H.pbe-rrkjus.UPF<br>B 1.0 B.pbe-n-van.UPF<br><br>CELL_PARAMETERS<br>11.03225111 0.49197118 -0.92807585<br>-0.15038487 5.49373010 -0.38883048<br>3.04894498 0.25407718 4.19633759<br><br>ATOMIC_POSITIONS {crystal}<br>Li 0.144228066000 0.155479905000 0.105275909000<br>Ca 0.911201719000 0.659605393000 0.179405853000<br> N 0.954182418000 0.066667349000 0.203452528000<br> H 0.879987796000 0.160521652000 0.398773311000<br> H 0.949093887000 0.150685763000 0.033727675000<br> H 0.590246767000 0.244749224000 0.483311768000<br> H 0.563997731000 0.067035740000 0.225636766000<br> H 0.437455407000 0.306433941000 0.454794956000<br> H 0.611216941000 0.379448807000 0.154202770000<br> H 0.231109967000 0.728337975000 0.002905585000<br> H
0.397236924000 0.644804127000 -0.037067236000<br> H 0.288752224000 0.877300760000 0.238936122000<br> H 0.231627436000 0.575300194000 0.301639728000<br> B 0.550495441000 0.249323405000 0.329678852000<br> B 0.288025902000 0.707564656000 0.123296526000<br><br>K_POINTS automatic<br>4 4 4 0 0 0<br><br><br></td></tr></table>