[gmx-users] emtol criterion

[Christos Deligkaris]

dear all,

I am trying to decide on a reasonable cutoff for emtol.

The Gromacs manual (section 3.10 on energy minimization) states that a
reasonable criterion for emtol can be found from the rms force a harmonic
oscillator would exhibit at room temperature (Equation 3.125). For a weak
oscillator (100 cm^-1) a force of 7.7 kJ/mol/nm is obtained. This number is
consistent with the default criterion of 10.0 kJ/nm/mol. It is not clear to
me how the value of 100cm^-1 was chosen in this example though.

Using a frequency of 1900cm^-1 and 7 amu reduced mass for CO stretching I
got 122 kJ/mol/nm which appears to be more consistent with the criterion of
1000 kJ/nm/mol used in the lysozyme tutorial:
http://www.mdtutorials.com/gmx/lysozyme/05_EM.html

In the literature I see the number of minimization steps (nsteps) reported
but not a specific criterion.

Any suggestions would be appreciated.

Best wishes,

Christos Deligkaris, PhD
Assistant Professor of Physics, University of Southern Indiana
SC2220, 8600 University Blvd, Evansville IN, 47712
Office Phone: (812) 228-5056
www.deligkaris.org @DeligkarisGroup