AMBER Archive (2003)

Subject: roar-cp : input for QM part ; output for CM2 charges

From: hagop demirdjian (hagop.demirdjian_at_ens.fr)
Date: Fri Jan 31 2003 - 09:38:29 CST

Hello AMBER users,
here are a few questions about roar-cp input/output

I am studying one HF molecule solvated in a box of TIP3P water. I am
running a QM/MM run with ROAR-CP where the QM part is just the HF molecule.

I used a frcmod file to build the HF molecule considering that partial
charges and spring constant for the bond were not important as they are
useless for the QM computation. I think that the only relevant
parameters are the Lennard Jones parameters in that case. Could someone
please confirm if I am right ?

About the output now,
my KEYWORD file reads the following

GEO-OK 1SCF GRAD ANALYT PRECISE PM3 CHARGE=0 MULLIK

I am surprised by the fact that the output gives the same partial CM2
charges as Mulliken analysis (see below).
Has anyone any explanation/suggestion for this ?

thank you for your help

    ATOMIC CHARGES:

    ATOM ELEMENTAL PARTIAL PARTIAL PARTIAL
     NO. SYMBOL MULLIKEN CM1 CM2
                      CHARGE CHARGE CHARGE

      1 F -0.21419 -0.26917 -0.21419
      2 H 0.21419 0.26917 0.21419

  TOTAL MULLIKEN CHARGE = 0.0000
  TOTAL CM1 CHARGE = 0.0000
  TOTAL CM2 CHARGE = 0.0000
  escf --> -71.1000422