[Pw_forum] about 'md'

Nicola Marzari marzari at MIT.EDU
Thu Dec 27 12:48:13 CET 2007

As a side note, if you have the positions along a trajectories,
you can reverse engineer the velocities:


(easy to see: do a series expansion of x(t), around t, in powers of
the timestep delta).


Paolo Giannozzi wrote:
> On Tuesday 25 December 2007 17:07, Dongdong Kang wrote:
>>   I want to use 'md' (in pwscf) to calculate vibrational property about
>> some materials. but when i check the output file, there aren't ion
>> velocities in it.   How can i get ion velocities in 'md' ?
> you have to modify PW/dynamics-module.f90 so that saves somewhere 
> the velocities (they should be in array "vel"). PWscf uses the plain verlet
> algorithm, not the velocity verlet. Until  now nobody has felt the need to
> know about velocities, so they were not saved
> Paolo

Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu

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