[CPMD-list] help on constrained MD

[Rongjian Sa]

Dear everyone,
I wander if who can tell me more about constrained MD calculation.
For a system contain ions A and B, if I just set the distance r= rAB as my reaction coordinate. 
And I discretize my reaction coordinate in 5 points, from 1.5 to 3 A (1.5, 2.0, 2.3, 2.5,3.0A)
After this procedure, I will perform MD simulation at these five points. Then I have get five
CONSTRAIN files. From every CONSTRAIN files, I would obtain the average force for
corresponding reaction coordinate. According the formula deltaF=integral Force(x)dx,
I should have two values as my integration area. But I do not how to decide these two 
values.  Also I want to know if I need integrate these five points. Then I  can 
get five energies and graph free energy vs distance. At last, I will obtain a curve and from
it I will get the free energy of systems.
I do know whether my procedure is correct. So I want to get your kind help!

Thank you!

Sincerely yours,
Rongjian Sa 
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