Hello

My question is under which conditions of NAMD QMMM the keyword

qmPointChargeScheme round Description: This option allows the user to decide if and how the point charges presented to the QM system will be altered. NONE: Nothing will be done. ROUND: This will change the most distant point charges so that the total sum of point charges is a whole number. ZERO: This will adjust the most distant point charges so that the total sum of point charges is 0.

should work?

My settings was

# QMPointChargeScheme none QMPointChargeScheme round     # qmCharge        "1 1"             # coupled with previous flag   # Info: 1) Group ID: 1 ; Group size: 80 atoms ; Total PSF charge: 1.5343 # FATAL ERROR: QM atoms do not add up to a whole charge, which is needed for PME.

or with 'qmCharge "1 1"" acivated. In both cases it failed the purpose. (one component of the system, i.e., one noncovalent ligand, was cut by ca 50%)

Thanks for advice

Francesco Pietra