AMBER Archive (2002)

Subject: Re: ntwv saves v(t) or v(t+dt/2) ?

From: David A. Case (case_at_scripps.edu)
Date: Thu Dec 19 2002 - 11:24:33 CST

On Thu, Dec 19, 2002, hagop demirdjian wrote:

> Just checking this : does the file mdvel contains velocities at t or at
> t+dt/2 ?
>
> I am asking this because the source file runmd.f contains the following
> comment :
>
> c
> c Note: if the last printed energy from the previous trajectory was
> c at time "t", then the restrt file has velocities at time
> c t + 0.5dt, and coordinates at time t + dt
> c----------------------------------------------------------------------------
> c
>
> but the manual does not mention the time at which velocity is saved, so
> I considered it was t until today...
>

The mdcrd and mdvel files are created at the same point in the code as is the
restart file. Hence the velocities are always a half time-step *behind*
the coordinates, as the comment above indicates.

..hope this helps...dac 

-- 

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David A. Case                     |  e-mail:      case_at_scripps.edu
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