[CPMD-list] Force on constraint.

[Yi LIU]

Dear everyone,

I am doing constrained CPMD. I want to get the free energy vs. reaction
coordinate (RC) by integrating the average force along RC. To do that, I
printed out forces on ions at every MD step and want to get mean forces
after time average. As a result, I found instantaneous 'forces on
constrained(fixed) ions' are all zero in every MD step. On the other hand,
the forces on free ions have some values but the averaged forces are closed
to zero. My questions are,

(1) Does CPMD compute forces on constrained ion, which are fixed in MD run?
(2) If answer of (1) is yes, does CPMD reset forces on constrained ion to
zero after computing force?
(3) How can I get forces on the constraint?

Thanks for any comments in advance.

Yi
----
Dr. Yi Liu
Department of Chemistry
The University of Western Ontario
London, Ontario, N6A 5B7, Canada

Email: yliu252 at uwo.ca
Phone: (519) 661-2111, ext. 88882
Fax:    (519) 661-3022