InSuk and I are having problems seeing energy conservation in simple
QM/MM calculations with the NDDO Hamiltonians. Out simplest example is
NMA in water, and here is a typical input file:
production
&cntrl
imin=0, ntx=7, ntpr=100,
ntf=2, ntc=2, tol=1.d-7,
ntb=1, ntp=0,
ntt=0,
nstlim=50000, dt=0.001, ntave=25000,
cut=9.0,
irest=1,
iwrap=1,
ifqnt=1,
/
&ewald
dsum_tol=1.d-6,
/
&qmmm
qmmask=':1', qmcharge=0, qm_theory='AM1',
scfconv=1.0d-11, tight_p_conv=1, peptide_corr=0,
/
This shows severe lack of energy conservation (change in total energy of
several dozen kcal/mol in just 50000 steps. If I set ifqnt=0, or
qm_theory="DFTB", then I get essentially no drift in total energy (i.e. less
than 0.1 kcal/mol over 50000 steps. I've attached the prmtop and inpcrd
files.
Does anyone see what is going wrong here? Our executables pass all the tests,
and the fact that DFTB seems to work but PM3 and AM1 fail is intriguing.
...thanks for any help...dac
_______________________________________________
AMBER-Developers mailing list
AMBER-Developers.ambermd.org
http://lists.ambermd.org/mailman/listinfo/amber-developers
Received on Tue Apr 05 2011 - 07:30:03 PDT
