AMBER Archive (2007)

Subject: AMBER: Fwd: SCC convergence failure in QM-MM DFTB

From: Francesco Pietra (chiendarret_at_yahoo.com)
Date: Sun Aug 26 2007 - 09:34:57 CDT

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
 1-4 NB = 0.0000 1-4 EEL = 0.0000 VDWAALS = 2754.0573
 EELEC = -18926.0584 EHBOND = 0.0000 RESTRAINT = 9.0684
 DFTBESCF= -11524.3870
 EAMBER (non-restraint) = -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
 1-4 NB = 0.0000 1-4 EEL = 0.0000 VDWAALS = 2856.2068
 EELEC = -21370.9526 EHBOND = 0.0000 RESTRAINT = 8.8248
 DFTBESCF= -11550.4178
 EAMBER (non-restraint) = -30065.1636
 ------------------------------------------------------------------------------

 SANDER BOMB in subroutine eglcao <qm2_dftb_eglcao.f> :
 SCC Convergence failure - MAXITER exceeded.
 Exiting

--- 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 QM-MM 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 98-atoms 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 6-31G*
> basis
> set level, with the same 98-atoms 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 QM-MM DFTB
> > To: Amber <amber_at_scripps.edu>
> >
> > Now the 98-atoms 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
> >
> >
> >
> >
>
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