[Pw_forum] Periodic boundary conditions

[Axel Kohlmeyer]

>>> "GN" == Gana Natarajan <gn203 at hermes.cam.ac.uk> writes:

GN> Dear PWScf authors,

dear gana,

GN> I wish to use Pwscf 2.1.1 to create a glass by cooling from the liquid 
GN> state.

GN> But I could not find in the MD routines, dynamics.f90 and vcsmd.f90, any 
GN> application of periodic boundary conditions (PBC's). These would be 
GN> required in order to shift back  atoms which leave the cell during the 
GN> MD and also to calculate the forces from the nearest image atoms.

don't worry. PBCs are active. in fact, PWScf uses a plane waves basis 
set which is only then very efficient when uses with crystals and other 
periodic systems. thus the usual problem is the other way around: you 
have to use a rather large system cell to avoid the side effect of
periodic image interactions in a slab or cluster calculation.

minimum image conventions, however, are usually not applied to
the trajectory of the atoms (this is true for other similar codes 
as well). if you need this, you can do this afterwards just as well.

best regards,
     axel.

GN> I notice that in FPMD there are PBC's, but I wish to use PWScf to
GN> perform Born-Oppenheimer surface dynamics.

GN> Please let me know if PBC's are already implemented or if they can be 
GN> added in the MD and variable-cell MD with a cubic cell.

GN> Thanks,

GN> Gana

GN> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
GN> Gana Natarajan
GN> Ph. D student
GN> Amorphous Materials Group
GN> Department of Chemistry
GN> Lensfield Road
GN> Cambridge CB2 1EW
GN> United Kingdom
GN> Tel: +44 -(01223) 336 532
GN> Fax: +44- (01223) 336 362

GN> _______________________________________________
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--
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Axel Kohlmeyer       e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.