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 - 09:00:03 PST
