From: Francesco Pietra (chiendarret_at_gmail.com)
Date: Tue Nov 23 2021 - 14:32:04 CST
Thanks for answering. Yes, this is a QM/MM of my organic molecule (QM) in
explicit CHCl3 (MM)
Now I removed both Opt and CPCM from the qmConfigLine. What happened is
like I described before, viewed with VMD from the QMonly dcd.
This corresponds to an explosion of the molecule, when the last ORCA
Cartesian coordinates are viewed with Jmol.
Still not clear to me why the different results from running QM with ORCA
in a continuum CPCM or QMMM with NAMD-ORCA in explicit CHCl3
On Tue, Nov 23, 2021 at 5:47 PM Mariano Spivak <mariano_at_ks.uiuc.edu> wrote:
> Hi Francesco,
> From this email, it is not quite clear what simulation you are trying to
> Is this a QM/MM of your organic molecule (QM) in explicit CHCl3 (MM)?
> If so, then you should not include implicit solvent in your QM
> calculation, because you already accounting for solute-solvent interactions
> through the NAMD interface.
> Also adding optimization to the QM/MM config line is not recommended to
> say the least. It defeats the purpose of the method and will give you wrong
> Hope this helps
> > On Nov 23, 2021, at 10:26 AM, Francesco Pietra <chiendarret_at_gmail.com>
> > An organic molecule of 28 CHON atoms could be optimized, with all
> positive frequency analysis, with latest ORCA 5 at level
> > PBE0 RIJCOSX D4 def2-TZVP Opt Freq tightscf defgrid2 CPCM (CHLOROFORM)
> > With QMMM 100 cycles in CHCl3, starting from an MD quasi equilibrated
> .pdb in that solvent, at level
> > PBE0 RIJCOSX D4 def2-TZVP defgrid2 enGrad CPCM
> > one of the tree rings of the molecule, and only that, underwent rapidly
> extreme distortion, even against the sp3 sp3 sp protocols.
> > Adding optimization (is that permitted with QMMM?), i.e., level
> > ## ORCA
> > # qmConfigLine "! MORead"
> > qmConfigLine "! PBE0 RIJCOSX D4 def2-TZVP Opt tightscf defgrid2 CPCM"
> > # qmConfigLine "%%moinp \"........gbw\""
> > qmConfigLine "%%maxcore 5000"
> > qmConfigLine "%%scf Maxiter 500 end"
> > qmConfigLine "%%geom Maxiter 500 end"
> > qmConfigLine "%%pal nproc 47 end"
> > qmConfigLine "%%output Printlevel Mini Print\[ P_Mulliken \] 1
> Print\[P_AtCharges_M\] 1 end"
> > rapid scf convergence was observed. However, at the ORCA GEOMETRY
> RELAXATION STEP
> > Warning: the length of the step is outside the trust region - taking
> restricted step instead
> > The input lambda is .... -862.826127
> > iter: 1 x= -888.315690 g= 0.656919 f(x)= 16.744573
> > ......................
> > ......................
> > iter: 101 x=-1512.546611 g= 0.000257 f(x)= 0.000000
> > [file orca_gstep/orca_gstep.cpp, line 790]: Error (ORCA_GSTEP): The
> lambda equations have not converged
> > Does that suggest any adjustment? After a couple of hours of thinking, I
> am short of ideas
> > Thanks for advice
> > francesco pietran MD
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