[CPMD-list] How to set the NOSE ELECTRONS parameters.

[HW Sheng]

Dear all, 

For an isobaric-isothermal MD simulation, I need to set the target electron kinetic energy. According to the manual, it's suggested to perform a short run without thermostats, and then take the "natural" electron kinetic energy as the target value (see, e.g, the CPMD manual, version 3.5.2 pp 62).  Still, I found this "target" value very capricious. After all, I arbitrarily set the kinetic energy to be 0.0001 a.u . During simulation I found that the output EKINC (the fictitious electron kinetic energy, ~ 0.007 a.u. after 1000 time steps) differs significantly from this desired kinetic energy 0.0001 a.u. I think this is abnormal, because EKINC should fluctuate around the desired (also predefined) kinetic energy. Can anyone tell me why?

The ion temperature is also a pain in the neck. I have tried a number of NOSE parameters, but the temperature fluctuation is still too much. For example, the target ion temperature is 5000 Kelvin, and the fluctuation reaches as much as 1000 K. A possible reason is that the target electron kinetic energy is set too small and causes the damping of the ions. Do I make any sense?

Besides, any rule-of-thumb to set the CELL kinetic energy? 
In a nutshell, I wish to have a guidance in choosing the Nose-Hover chain parameters. I appreciate your help.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://cpmd.org/pipermail/cpmd-list/attachments/20021115/290ecbd7/attachment.html