Re: About restarting QM-MM simulation

From: Marcelo C. R. Melo (
Date: Wed Feb 13 2019 - 12:31:57 CST

NAMD does not control ORCA in terms of pausing and resuming an SCF
calculation, so there is nothing in NAMD's config or restart file that
would inform ORCA of where it sopped, and how should it resume.
NAMD QM/MM can only be paused/resumed between MD steps, which is were you
will have "restart" files written. (In your case, given your "restartfreq",
every 100 MD steps). For QM/MM simulations to be properly managed by NAMD,
your QM calculation needs to "fit" inside MD steps.

Marcelo Cardoso dos Reis Melo, PhD
Postdoctoral Research Associate
Luthey-Schulten Group
University of Illinois at Urbana-Champaign
+1 (217) 244-5983
On Wed, 13 Feb 2019 at 09:34, Francesco Pietra <>
> Hello
> How can NAMD-ORCA QM-MM simulations be correctly restarted? I mean in the
> context of namd.config in Example1 tutorial:
> structure       XXX_A1_box_ion.psf
>> coordinates     XXX_A1_box_ion.pdb
>> # Output Parameters
>> binaryoutput    no
>> outputname      XXX_A1_out
>> outputenergies  1
>> outputtiming    1
>> outputpressure  1
>> binaryrestart   yes
>> dcdfile         XXX_A1_out.dcd
>> dcdfreq         1
>> XSTFreq         1
>> restartfreq     100
>> restartname     XXX_A1_out.restart
> In particular when no SCF convergence was not yet reached (in favorable
> cases, info says that SCF convergence is close to be reached), so that
> XXX_A1_out.restart was not provided.
> I was also unable to find on ORCA manual how to increase the number of SFC
> iterations above the default 125.
> Thanks for advice
> francesco pietra
> PS I understand that the ORCA calculation can be carried out separately
> but I have some reasons now to let NAM-ORCA working together.

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