On Sun, Oct 04, 2015, Sofia Vasilakaki wrote:
>
> 1. Has anyone tried to run QM/MM with API using Orca 3.0.3?
We've used 3.0.1 quite a bit. I don't see that there should be any
differences with 3.0.3, but please let us know if you find a version-specific
problem.
>
> 2. In this paper J. Comp. Chem. 2014, 35, 95-108 since there is a
> carboxylate group in the QM area (guessing is deprotonated), why diffusion
> is not added in the basic set? My ligand has a deprotonated carboxylate
> group so I was thinking of using 6-31+G*. Also, although in Amber14,
> ff99SB is mentioned. Why not ff12SB?
I recommend using a template file for "external" QM/MM calculations. That
allows you to completely specify what you want (basis sets, specific
functionals, SCF convergence parameters, etc.)
>
> 3. In the supporting info of this paper, the calling convention is
> mentioned (get_orc_forces) but I don't understand whether this should be a
> part of the input QM/MM file and how the format should be. An example
> would be really helpful.
Our servers are down now, but I'm cc-ing this to He Chen, who should
be able to post an example input when our machine return to service.
>
> 4. The recommended production time for a QM/ΜΜ calculation?? It is a bit
> slow. Although I found Orca extremely easy to use (first time I hit enter
> in the command line and the command is being executed immediately without
> any further arguments! Sweet...), the performance is not great so there is
> a limitation.
I'm tempted to say: "welcome to quantum chemistry". The time spent per step
using QM/MM is generally dominated by the QM part, which should be the same
as if you did the same size of QM problem using orca directly. Many
simulations that one would like to do are simply too time-consuming.
This is a fairly general answer, but the question itself was pretty vague...
...good luck...dac
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Received on Sun Oct 04 2015 - 11:30:05 PDT
