Forces in QM/MM calculations

Date: Wed Apr 08 2020 - 12:57:07 CDT

Dear collegues,

I have a question regarding the forces in NAMD. I am running NAMD-gaussian
QM/MM dynamics, but for a test I left only QM part, i.e. in fact I am
running QM dynamics. I write forces to the Force.dcd file. Thus, I assume
that the forces printed in Force.dcd file are the QM-calculated forces, am
I right?

I have a few question regarding "QM" calculation in NAMD: in the .log file
I have both the SCF energy and the total potential energy, which are a bit
different. For my 57-atomic system:
SCF energy: -573116.738382
KINETIC: 34.5168
TOTAL: -537086.8908
POTENTIAL: -573121.4067
BOND: 0, ANGLE: 0, DIHED: 0, INPRP: 0, ELECT: -166.7534
VDW: 0; BOUNDARY: 0; MISC: -572954.6542

What are the correlations between SCF energy and the TOTAL energy in my
case? Is it the gaussian-calculated energy or the NAMD-calculated energy
with amber force field?
Also, as I understand MISC term is for some "external electrical field",
but I do not have an external electrical field. Why then do I have such a
huge MISC term? And how is the ELECT term calculated in my case?

Thank you in advance,

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