[Pw_forum] on variable cell optimization
Serge Nakhmanson
nakhmans at physics.rutgers.edu
Fri Jan 28 20:48:19 CET 2005
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1
Paolo Giannozzi wrote:
> On Friday 28 January 2005 16:58, Serge Nakhmanson wrote:
>
>
>> Entering Dynamics; it = 28 time = 0.00131 pico-seconds
>>[...]
>>Nothing is moving, nothing is changing.
>
>
> in 1.31 fs very little is happening, for sure
>
>
Dear Paolo,
Thank you very much for your advice. I understand now what I did
wrong. I did not realize that a timestep is actually attached to
a vc-relax calculation (when I do fixed volume relax there is no
timestep attached to it). I thought dt has to be set only if I
do md or vc-md. A timestep of ~ 0.05 fs is surely too small.
>>Or is my cell too heavy (see below)?
>
>
> you used the default value for the time step (1 a.u.=0.0484fs): it is
> way too small. There shouldn't be a default value for the time step
> in the first place. There is one for the cell mass, and it should be good
> for most purposes.
Then I was a bit confused by the documentation. This is what is
written it INPUT_PW:
wmass REAL
ficticious cell mass for variable-cell md simulations
- From this I assumed that there is no default for wmass and I do
have to set it something.
>
>>BTW, what is the UMA unit ( cell mass = 36.00000 UMA )?
>
>
> atomic mass units, I guess: mass of H=1
>
Shouldn't we call it AMU or AUM then? :)
S.
- --
******************************************************************************
Serge M. Nakhmanson phone: +1 (732) 445-4603
Postdoctoral RA fax: +1 (732) 445-4400
Department of Physics & Astronomy
Rutgers, The State University of New Jersey
136 Frelinghuysen Road nakhmans at physics.rutgers.edu
Piscataway, NJ 08854-8019 http://www.physics.rutgers.edu/~nakhmans/
My GnuPG public key is here:
http://www.physics.rutgers.edu/~nakhmans/PGP/nakhmans_pubkey_current.asc
******************************************************************************
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.2.1 (GNU/Linux)
Comment: Using GnuPG with Thunderbird - http://enigmail.mozdev.org
iD8DBQFB+pcDS2Ygfv2TcL8RAnKCAJ938kGhfdBVcusZydznslomjqXmfQCcDKvl
I0WD+DS6w3IfsHO8lMuBPbk=
=vR87
-----END PGP SIGNATURE-----
More information about the Pw_forum
mailing list