**From:** himanshu chandola (*beu99419_at_ccsun50.iitd.ernet.in*)

**Date:** Fri Jan 30 2004 - 01:28:51 CST

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hi all -

referring to the rotating constraints feature in namd. We know

that the force is 2K(R-X). Now R is the current reference position

which should hence lie in the rotational circle in which we rotated the

atom - and as we've already given the angular velocity of rotation we

already know the current reference position at any time.

My problem is about X. Now though the manual doesn't say it - X should be

the current position of the atom(i'm sorry if i'm wrong and ofcourse all

these quantities are vectors).

My problem is in calculating the torque which i've put on each atom.

Though it appears easy to do - how can the torque be zero if i have put my

spring constants so stiff that the atoms being rotated follow their

reference point very closely.

Now - i am sure that i am wrong somewhere - could you please point out

where i am wrong - and hence how the torque applied on the atom

calculated.

thanks

himanshu

iit delhi

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