[Pw_forum] How to change velocities of specified ions ?

lan haiping lanhaiping at gmail.com
Sat Mar 7 11:31:53 CET 2009

Dear All,

  I am intending to examine a structure evolution by certain elastic
scattering, such as ion bombs, high spread electrons.
Therefore, I need to add some kinetic energies for some ions after some
times .  I checked the INPUT_CP and found it may  meet my intent, and i
would like to make clear for some points I donot understand well. Could you
please give me some hints or suggestions on this issue ?

 1,  I think  I can simulate the scattering process through changing ions'
velocities. The card for velocities : ion_velocities has several options
such as "default", "change step", "random", "from_input" and "zero".
If I just want to  change some ions' states and keep others, which option
should I  choose ?  My first guess is "from_input".
It seems that i can get the finnal values of ions
for  previous simulation , then change these values and specify in the
ATOMIC_VELOCITIES. Is it OK for me to simulate this scattering process ? Do
I lose some points ?
 2, About electron_velocities.  For elastic scattering on ions,  should i
consider the change of electron_velocities ?     I am not very clear about
this tag, would you please explain which  physical process this tag account
for ?


Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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