Defult value of Beta in Modified short-range interactions with Ewald summation (p. 365, man 2022.1)

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1

GROMACS version: 2022.1
GROMACS modification: Yes/No
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While calculting the short range coulombing interaction using ewald method, what is the default value of beta used by gromacs? Where, beta is a parameter that determines the relative weight between the direct space sum and the reciprocal space sum (page 365of gromacs mannual 2022.1).

We can’t give beta as an input ([gmx-users] relative weight between the direct space sum and reciprocal space sum).

Thanking you,
Prashil

2

There is no default value for beta. It is set indirectly with ewald_rtol and rcoulomb.

3

Thanks hess.
May I ask for the relation between ewald_rtol and rcoulomb. Since I am calculating the Coulomb(SR) manually and crosschecking the same with Gromacs (for a single molecule in a box), I need the value of Beta that gromacs have used. I am using
ewald-rtol = 1e-05
rcoulomb = 0.95
Box length (cubic) = 2.0 nm

4

Please read the manual before asking such questions. It’s formula 167 on this page:
https://manual.gromacs.org/current/reference-manual/functions/nonbonded-interactions.html#modified-short-range-interactions-with-ewald-summation

Also mdrun prints beta for your simulation in the md.log file.