[Pw_forum] vc-md question

[Miguel Martínez Canales]

Hi again, Paolo

> I think that there is presently no check on convergence, so if you 
> keep sending jobs, it will keep running. Does it converge or not?

Ok, so there is no check. I should have known better. Use the source, Luke.
Regarding convergence, it starts closing (slowly if dt is not good,
obviously) and then it oscillates. Or that is what it seems. Some output at
the end of the e-mail.

> By the way, there is also a 'vc-relax' option that is supposed to 
> perform structural optimization. I am not sure if vc-md can
> actually do damped dynamics

I understood that vc-relax fully relaxes the structure. I mean, the target
pressure of the relaxation is p=0. That is why I used vc-md. How do you
compute equations of state for noncubic cells? Because maybe I am working
in a very ineffective way.

Oh! and vc-md not being damped might explain the following output:

Input is the same as in first e-mail, but dt=100 (note: dt=150 leads to
structure deestabilisation) and the following &system flags and ATOMIC_POS:

#####################
&system
    ibrav=  7, celldm(1) =6.163307, celldm(3)=1.2845405, nat=  5, ntyp= 2,
...
&cell
    cell_dynamics='w'
    press=760.0
    cell_factor=1.5
/
...
H    0.00   0.00   0.474478194
H    0.00   0.00  -0.474478194
#####################

Output (long and boring):
$ grep  bohr** geh4.scf.out
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.49
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.78
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.12
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.52
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.82
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.42
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.61
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.44
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.40
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.71
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.74
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.80
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.27
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.49
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.06
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.14
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.93
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.75
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.83
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.55
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.64
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.39
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.76
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.62
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.54
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.44
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.63
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.54
       total   stress  (ryd/bohr**3)                  (kbar)     P=  758.71
       total   stress  (ryd/bohr**3)                  (kbar)     P=  758.70
       total   stress  (ryd/bohr**3)                  (kbar)     P=  758.93
       total   stress  (ryd/bohr**3)                  (kbar)     P=  758.87
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.46
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.23
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.58
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.60
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.92
       total   stress  (ryd/bohr**3)                  (kbar)     P=  759.90
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.20
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.47
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.19
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.54
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.84
       total   stress  (ryd/bohr**3)                  (kbar)     P=  760.80


-- 
----------------------------------------
Miguel Martínez Canales
    Dto. Física de la Materia Condensada
    UPV/EHU
    Facultad de Ciencia y Tecnología
    Apdo. 644
    48080 Bilbao (Spain)
Fax:  +34 94 601 3500
Tlf:  +34 94 601 5437
----------------------------------------

"I don't think that Debian can really compete with
Gentoo. Sure it might be okay, but when it comes to
dependencies, you probably are still going to have
to get them all on your own. Or is there something
like portage in the Debian world as well?"

Annonymous