[CPMD-list] Bad results during the heating phase of a md run

[Axel Kohlmeyer]

On Tue, 23 Aug 2005, Reinaldo Pis Diez wrote:


reinaldo,

[...]

RPD> Zion = 9 and PBE xc functional. I've made some previous tests with the 
RPD> sodium dimer and found that 60 Ry for PW cutoff are ok to reproduce 
RPD> the bond distance, for example. Then, I turn to the sodium hexamer. I 
RPD> use a simulated annealing procedure to optimize the wavefunction 
RPD> (na6_wfn.inp and na6_wfn.out files) and it seems to be alright. Then, 
RPD> the hexamer is allowed to heat up to 600 K. The lattice of the (cubic) 
RPD> cell was 15 A and the PW cutoff was 60 Ry as said above. The md run 
RPD> diverges from the second time step. I increased the lattice cell and 

this is because you did not read the coordinates (and velocities)
of your atoms from the restart file, so the wavefunction did not
match the positions of your coordinates. note that you have a significant
temperature of the ions (TEMPP) in your annealing. (btw. is there are 
reason that you use that instead of optimizing the wavefunction with
ODIIS of PCG?). so you either have to add COORDINATES (and VELOCITIES)
to the RESTART line in your MD or add the following to the annealing 
input in the &ATOMS section:

CONSTRAINTS
 FIX ALL ATOMS
END CONSTRAINTS


RPD> the PW cutoff to 25 A and 70 Ry, respectively, to see where the 
RPD> problem is but I got the same results (na6_md_ini.inp and 
RPD> na6_md_ini.out files). I can see from the output that EKINC is going 
RPD> large at the very beginning of the run but I don't know if this could 
RPD> be a clue and how to handle it to  get the simulation running. Any 
RPD> help will be very appreciated. The input and output files are appended.
RPD> 		Sorry for the long mail but I cannot figure out how to explain my 
RPD> problem in few words.

no problem.

best regards,
	axel.


RPD> 		Thanks in advance.
RPD> 		Regards,
RPD> 
RPD> 						Reinaldo
RPD> 

-- 

=======================================================================
Dr. Axel Kohlmeyer   e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.