[CPMD-list] velocity output

[Axel Kohlmeyer]

On Fri, 7 Sep 2007, liu liuxiandong wrote:


XL> Dear CPMDers,

dear xiandong liu,

XL>   I want to extract the vibration properties of some atom species from the
XL> velocity correlation function along the MD simulation. I find that the
XL> output TRAJECTORY file contains all ionic positions and velocities, so the
XL> file is huge for a MD trajectory lasting several picoseconds. Could CPMD
XL> outputs the velocities of the atom type specified by the user ? Any
XL> suggestion is appreciated .

in principle this is possible, but you have to modify the sourcecode
for that. however, is wonder whether this is worth the effort. 
if you can afford to run a long trajectory of a large system, so that 
the total storage requirement would really matter, you can also afford
to have extra (external?) disk storage for keeping and analysing your
trajectory. in comparison to equivalently costly classical MD 
calculations or even coarse-grained MD, the disk size requirements for
a CPMD trajectory will always be miniscule.

please keep in mind, that it is good practice to split CPMD runs into 
segments and then build a continous trajectory through restarting. 
if you rename the outputs/files after each segment (which is actually 
good practice and highly recommended) you will have a series of 
shorter files that will be easier to post-process.

cheers,
   axel.


XL> 
XL> 
XL> 
XL> Xiandong Liu
XL> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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