Hi Giovanni,
Semiempirical QM energies in Amber (sqm and QM/MM via sander) are heats of formation. Orca instead reports the total electronic energy (including core repulsion). Hence what you observe should be the difference between electronic energy and heat of formation. The energy difference between two snapshots should be identical.
All the best,
Andy
—
Dr. Andreas W. Goetz
Assistant Research Scientist
San Diego Supercomputer Center
Tel: +1-858-822-4771
Email: agoetz.sdsc.edu
Web: www.awgoetz.de
> On Feb 1, 2019, at 8:55 AM, GiovanniMaria Piccini <giovannimaria.piccini.gmail.com> wrote:
>
> Dear all,
>
> I have noticed large differences between the semiempirical energies between
> AMBER internal PM3 and Orca PM3 used as external QM potentail.
> Here I report the results of a single point energy evaluation given an
> external trajectory, i.e. the same structure is evaluated.
> I use the same parameters for the two calculations that differ only for the
> way the QM part is calculated (see below).
>
> AMBER PM3:
>
> FINAL RESULTS
>
>
>
> NSTEP ENERGY RMS GMAX NAME NUMBER
> 1 -5.1000E+03 1.3733E+01 5.9035E+01 C 1
>
> BOND = 0.0000 ANGLE = 0.0000 DIHED =
> 0.0000
> VDWAALS = 771.4407 EEL = -5669.3000 HBOND =
> 0.0000
> 1-4 VDW = 0.0000 1-4 EEL = 0.0000 RESTRAINT =
> 0.0000
> PM3ESCF = -202.1858
> minimization completed, ENE= -.51000451E+04 RMS= 0.137329E+02
> minimizing coord set # 2
>
>
> AMBER/Orca PM3
>
> FINAL RESULTS
>
>
>
> NSTEP ENERGY RMS GMAX NAME NUMBER
> 1 -2.6309E+04 1.3753E+01 5.7750E+01 O 280
>
> BOND = 0.0000 ANGLE = 0.0000 DIHED =
> 0.0000
> VDWAALS = 771.4407 EEL = -5669.3000 HBOND =
> 0.0000
> 1-4 VDW = 0.0000 1-4 EEL = 0.0000 RESTRAINT =
> 0.0000
> EXTERNESCF = -21411.2247
> minimization completed, ENE= -.26309084E+05 RMS= 0.137530E+02
> minimizing coord set # 2
>
>
> The two input read:
>
> AMBER PM3:
>
> Production
> &cntrl
> imin=5,
> maxcyc=1,
> ntx=1,
> ntpr=1,
> ntwx=1,
> cut=8.0,
> ntb=1,
> ntp=0,
> ntt=3,
> gamma_ln=2.0,
> ig=-1,
> ifqnt=1,
> plumed=1,
> plumedfile='plumed.dat'
> /
> &qmmm
> qmmask='.1-6',
> qmcharge=-1,
> qm_theory='PM3',
> qmshake=1,
> qm_ewald=0,
> qmmm_int=1
> /
>
> AMBER/Orca PM3:
>
> Production
> &cntrl
> imin=5,
> maxcyc=1,
> ntx=1,
> ntpr=1,
> ntwx=1,
> cut=8.0,
> ntb=1,
> ntp=0,
> ntt=3,
> gamma_ln=2.0,
> ig=-1,
> ifqnt=1,
> plumed=1,
> plumedfile='plumed.dat'
> /
> &qmmm
> qmmask='.1-6',
> qmcharge=-1,
> qm_theory='EXTERN',
> qmshake=1,
> qm_ewald=0,
> qmmm_int=1
> /
>
> &orc
> method ='pm3',
> basis ='svp',
> convkey='TIGHTSCF',
> /
>
> As it can be observed there is an order of magnitude difference between the
> two energies and this depends, I believe, on the QM energy.
> May it also be the subtractive scheme?
> I need to fix this because when have to use DFT method with Orca and
> compare them with AMBER semiempirical I must be sure I am comparing the
> same quantities.
>
> I am using AMBER 17 and Orca/4.0.0
>
> Thank you in advance,
> Giovanni
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Received on Fri Feb 01 2019 - 11:30:03 PST
