[CPMD-list] some question on NOSE CAFES.

[Axel Kohlmeyer]

On Sun, 25 Feb 2007, Tengfei Luo wrote:

TL> Dear all:
TL> I'm simulating the thermal energy equilibrating on a 64 Si atoms system.
TL> 

TL> Here comes the questions: How can I check whether each of the two
TL> part is at there set temperature? or how to monitor the temperatures
TL> of the two parts separately? Do I need to modify the code? or there
TL> is some other software can analyze the trajectory to see the
TL> temperature of different parts of a system?

no, you only need to read the manual:

 A new file, \texttt{CAFES} is created containing the temperature
      of each group (cols. 2 \dots \textsl{ncafesgrp+1}) and the energy
      of the Nose-Hoover chains of that group (last columns).\\
      Using CAFES with different temperatures only makes sense if the
      different groups are decoupled from each other by increasing the
      masses of the involved atoms. The


TL> Another question is that after I began the CP-MD steps, it took 5000
TL> steps before the atoms start to move(please see the following part
TL> of the output). Why does this happen?

if your structure is in the potential energy minimum (or close to it)
and you assign no initial temperature, where should the kinetic energy
come from?? why _should_ the atoms move at all? 
check out the TEMPERATURE keyword. (RTFM again).

[...]
TL> 
TL> Sorry for the long email! Any suggestion or advice would be greatly appreciated!

well, you could have just copied smaller parts of the output,
e.g. beginning and end of the trajectory. the message would 
have been the same.

cheers,
   axel.

TL> 
TL> Regards,
TL> 
TL> T.Luo

-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.