# amber-developers: pressure code

From: Thomas Cheatham III <tec3.utah.edu>
Date: Tue, 27 May 2008 13:17:53 -0600 (Mountain Standard Time)

Howdy all! We are interested in doing pressure scaling only in a single
dimension for some salt/water interface studies. Looking at the code, it
looks like we can simply change the scaling code in runmd.f to only do the
scaling in 1-D. Although this will obviously require longer to
equilibrate, I do not see any obvious problem in doing this... Am I
missing something? Is there something to worry about with holonomic
corrections and/or virials/forces?

[Of course this assumes an orthorhombic box and also assumes not running
PIMD or AMOEBA].

In the meantime, we'll run with it in tests on small water boxes and see
if anything disasterous happens.

--tom

Current code:

if (ntp == 1) then
rmu(1) = (1.d0-dtcp*(pres0-pres(4)))**third
rmu(2) = rmu(1)
rmu(3) = rmu(1)
else if (ntp > 1) then
rmu(1) = (1.d0-dtcp*(pres0-pres(1)))**third
rmu(2) = (1.d0-dtcp*(pres0-pres(2)))**third
rmu(3) = (1.d0-dtcp*(pres0-pres(3)))**third
end if

if (ntp == 1) then
rmu(1) = (1.d0-dtcp*(pres0-pres(4)))**third
rmu(2) = rmu(1)
rmu(3) = rmu(1)
else if (ntp == 2) then
rmu(1) = (1.d0-dtcp*(pres0-pres(1)))**third
rmu(2) = (1.d0-dtcp*(pres0-pres(2)))**third
rmu(3) = (1.d0-dtcp*(pres0-pres(3)))**third
else if (ntp == 3) then ! scale only X direction
rmu(1) = (1.d0-dtcp*(pres0-pres(4)))**third
rmu(2) = 1.d0
rmu(3) = 1.d0
end if

\-/ Thomas E. Cheatham, III (Assistant Professor) College of Pharmacy
-/- Departments of Med. Chem. and of Pharmaceutics and Pharm. Chem.
/-\ Adjunct Asst Prof of Bioeng.; Center for High Performance Computing
\-/ University of Utah, 30 S 2000 E, SH 201, Salt Lake City, UT 84112
-/-
/-\ tec3.utah.edu (801) 587-9652; FAX: (801) 585-9119
\-/ BPRP295A http://www.chpc.utah.edu/~cheatham
Received on Wed May 28 2008 - 06:07:56 PDT
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