Re: changing value of coulomb constant

From: Gumbart, JC (gumbart_at_physics.gatech.edu)
Date: Mon Apr 15 2019 - 09:05:29 CDT

What about changing the dielectric constant, which is a NAMD-accessible parameter?

Best,
JC

On Apr 14, 2019, at 12:47 PM, Brian Radak <brian.radak_at_gmail.com<mailto:brian.radak_at_gmail.com>> wrote:

Unfortunately this is not commonly done and requires a bit of an expert touch. All internal evaluations in NAMD use the precompiler definition COLOUMB inside src/common.h. You will have to change this value and recompile.

Note that you might still have a little bit of trouble depending on your force field and input file format. The AMBER file format (and the extended format for the CHARMM force field) implicitly uses its own value of COULOMB (actually, the sqrt of it). A similar thing happens for the CHARMM Drude force field in PSF format.

HTH,
BKR

On Sun, Apr 14, 2019, 2:28 AM Akshay Prabhakant <akshayresearch16_at_gmail.com<mailto:akshayresearch16_at_gmail.com>> wrote:
Hello everyone,
I am dong a comparison study for a protein system using AMBER-MD and NAMD, using amber parameters, and for that I need to change the value of NAMD coulomb constant. How can I change the value of the coulomb constant if I have downloaded the NAMD_Linux-x86_64-multicore ?

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