AMBER Archive (2007)Subject: Re: AMBER: Fwd: SCC convergence failure in QMMM DFTB
From: Francesco Pietra (chiendarret_at_yahoo.com)
Date: Sun Aug 26 2007  11:28:14 CDT
The last MD (second addendum) was carried out as initially, according to minin
amd mdin shown at the start of the thread. The only difference (second
addendum) was a (a) larger Cap and (b) DFT minimization with NWChem of the
structure used before, which came from MMFF94 global conformational search in
vacuum plus amber simulated annealing in vacuum; the two converged to the same
minimum, which I took for absolute minimum.
The suggestion about WAT rearrangement is something that I also vaguely
conceived for the same reasons that Bud made explicitly. Comforted by this,
I'll try (starting from the DFT minimized structure) first classical minin and
mdin, then repeating dftb minin and mdin as before. If not reported further, it
means that "classical" has solved the problem.
Thanks
francesco
 "M. L. Dodson" <mldodson_at_houston.rr.com> wrote:
> Francesco Pietra wrote:
> > Second addendum to the original (Subject) issue:
> >
> > Using a larger solventCap (25.0) and starting from pdb file for the solute
> > which had been minimized by "ab initio" DFT with the most recent
> functionals
> > with NWChem, sander bombed for the same reason somewhat earlier than with
> cap
> > 20.0 and stating from pdb minimized by global conformational space MMFF94
> and
> > Amber9 simulated annealing. I add also the two last steps in the
> presumption
> > they may help. DFTBESCF is about the same as for Cap 20.0, while all other
> > energy values are higher (for 1951 WAT residues added for Cap 25.0, with
> > respect to 947 residues for Cap 20.0). If useful, I add that DFT as said
> above
> > never crashed.
> >
> >
> > NSTEP = 2600 TIME(PS) = 5.200 TEMP(K) = 299.15 PRESS =
> 0.0
> > Etot = 24120.4790 EKtot = 3566.8407 EPtot =
> 27687.3196
> > BOND = 0.0000 ANGLE = 0.0000 DIHED =
> 0.0000
> > 14 NB = 0.0000 14 EEL = 0.0000 VDWAALS =
> 2754.0573
> > EELEC = 18926.0584 EHBOND = 0.0000 RESTRAINT =
> 9.0684
> > DFTBESCF= 11524.3870
> > EAMBER (nonrestraint) = 27696.3881
> >
>

> >
> >
> > NSTEP = 2700 TIME(PS) = 5.400 TEMP(K) = 300.31 PRESS =
> 0.0
> > Etot = 26475.7499 EKtot = 3580.5889 EPtot =
> 30056.3388
> > BOND = 0.0000 ANGLE = 0.0000 DIHED =
> 0.0000
> > 14 NB = 0.0000 14 EEL = 0.0000 VDWAALS =
> 2856.2068
> > EELEC = 21370.9526 EHBOND = 0.0000 RESTRAINT =
> 8.8248
> > DFTBESCF= 11550.4178
> > EAMBER (nonrestraint) = 30065.1636
> >
>

> >
> > SANDER BOMB in subroutine eglcao <qm2_dftb_eglcao.f> :
> > SCC Convergence failure  MAXITER exceeded.
> > Exiting
> >
> >
>
> To incorporate an answer to Professor Roitberg within a reply to
> you, sander in amber9 cannot do box/PME simulations.
>
> Now on to your simulation. I think we need some preliminary
> answers, first. How did you get the structure you started with?
>
> Professor Roitberg's suggestion to start with a structure that had
> been minimized with AM1 seems to me a good one. Then you might
> try a preliminary VACUUM SCCDFTB minimization. If you cannot get
> a SCF in vacuum, you are unlikely to get one with a water cap,
> either.
>
> The output given seems to indicate that the energy is dropping by
> ~2500 over a hundred steps, and coupled with the lack of major
> changes in the QM energy, would seem to me to indicate the solvent
> is doing some rearrangement. This would also seem to me to be
> unrelated to the inability to achieve SCF, but I am open to
> other suggestions by the QMMM experts that might read this posting.
>
> This output is from an MD run. Did you not minimize the system
> and do classical MD to relax the system to the force field? At
> the very least you need some time with the classical FF to relax
> the solvent voids created by LEaP. We need more information on
> what you have done. In detail. Otherwise we are all just wasting
> time.
>
> Bud Dodson
>
> >
> >
> >
> >  Francesco Pietra <chiendarret_at_yahoo.com> wrote:
> >
> >> Date: Sun, 26 Aug 2007 00:26:42 0700 (PDT)
> >> From: Francesco Pietra <chiendarret_at_yahoo.com>
> >> Subject: Fwd: SCC convergence failure in QMMM DFTB
> >> To: Amber <amber_at_scripps.edu>
> >>
> >> Perhaps relevant to add to the issue below:
> >>
> >> solvateCap EQE TIP3PBOX {coordinates of a solute central atom} 20.0
> >>
> >> placed the solute right at the center of the spherical cap; though, along
> the
> >> longer axis, the 98atoms solute was not far from the spherical cap edge.
> I
> >> wonder whether a much bigger cap should be set, and whether 20.0 present
> one
> >> has hindered SCC convergence.
> >>
> >>  I was surprised that DFTB MD used as as little memory as AM1 MD (ca
> 0.1%
> >> of
> >> the 4GB available per node). Having not yet read the DFTB theory in
> detail, I
> >> am comparing to classical DFT, where modern functionals at modest 631G*
> >> basis
> >> set level, with the same 98atoms molecule in vacuum, led to use all the
> >> available memory (ad there was still much swapping). I understand that
> DFTB
> >> working must be profoundly different from classical DFT.
> >>
> >> francesco
> >>
> >>  Francesco Pietra <chiendarret_at_yahoo.com> wrote:
> >>
> >>> Date: Sat, 25 Aug 2007 10:54:12 0700 (PDT)
> >>> From: Francesco Pietra <chiendarret_at_yahoo.com>
> >>> Subject: SCC convergence failure in QMMM DFTB
> >>> To: Amber <amber_at_scripps.edu>
> >>>
> >>> Now the 98atoms solute is well inside TIP3PBOX cap (prepin from
> >>> antechamber).
> >>> After successful minimization with:
> >>>
> >>> Initial min for qmmm with dftb
> >>> &cntrl
> >>> imin=1, maxcyc=500, ncyc=200,
> >>> cut=20.0, ntb=0, ntc=2, ntf=2,
> >>> ivcap=0, fcap=10,
> >>> ifqnt=1
> >>> /
> >>> &qmmm
> >>> qmmask=':1',
> >>> qmcharge=0,
> >>> qmtheory=7,
> >>> qmshake=0,
> >>> qm_ewald=0
> >>> /
> >>>
> >>> MD with:
> >>>
> >>> 300K constant temp for qmmd with dftb
> >>> &cntrl
> >>> imin=0, ntb=0
> >>> cut=20.0, ntc=2, ntf=2,
> >>> tempi=300.0, temp0=300.0,
> >>> ntt=3, gamma_ln=1.0,
> >>> nstlim=20000, dt=0.002,
> >>> ivcap=0, fcap=10,
> >>> ntpr=100, ntwx=100,ifqnt=1
> >>> /
> >>> &qmmm
> >>> qmmask=':1',
> >>> qmcharge=0,
> >>> qmtheory=7,
> >>> qmshake=0,
> >>> qm_ewald=0
> >>> /
> >>>
> >>> sander.MPI (mpirun np 4) exited because:
> >>>
> >>> vlimit exceeded for step 2886; vmax = 26.4356
> >>> SANDER BOMB in subroutine eglcao <qm2_dftb_eglcao.f> :
> >>> SCC Convergence failure  MAXITER exceeded.
> >>> Exiting
> >>>
> >>> Much obliged for suggestions what to do best. Thanks
> >>>
> >>> francesco pietra
> >>>
> >>>
> >>>
> >>>
> >
> 
> M. L. Dodson
> Email: mldodsonathoustondotrrdotcom
> Phone: eight_three_twofive_63386_one
> 
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