I second the suggestion to contact Gaussian; Dr. Clemente over there, for example, is extremely helpful.
But, I can still offer a few comments:
1) In the g16 directory there should be an “amber.prm” file. From that file you can see what the syntax is for specifying the parameters in your frcmod. You can then write a script or modify the TAO scripts to put the information in your frcmod into the needed format. Please note that the hard-coded amber parameters in g16 are ancient (I believe they are from parm96.dat).
2) Check out the ModQ3M approach by Dr. Gascon (my former Ph.D. adviser): http://gascon.chem.uconn.edu/software <http://gascon.chem.uconn.edu/software>. The software goes beyond your immediate interests, but the first few steps guide you through setting up an ONIOM calculation with extra/custom parameters in the ONIOM input. You’ll need to convert your structure into a TINKER XYZ; from there, with some additional files, there is a utility that will convert the TINKER xyz into an ONIOM input. It’s not an easy process, but it works.
3) If you are planning on running a single point calculation, there is no need to set up an ONIOM input; you can simply specify the environment as a background charge distribution. If you plan on doing geometry optimizations, I recommend going through the labor of setting up an ONIOM calculation. However, for quick and dirty work, you could fix an atom of your QM region to pin it down, so to speak, and just use background point charges for the environment. This approach may or may not be a good approximation, depending on how important steric strain (mechanical distortion) imposed by the environment on the QM region is for your system.
Best,
Matthew
> On Apr 7, 2022, at 12:58 PM, David A Case <david.case.rutgers.edu> wrote:
>
> *Message sent from a system outside of UConn.*
>
>
> On Thu, Apr 07, 2022, Kovács Richárd Dezső wrote:
>>
>> I'm working on an ONIOM calculation of an enzyme reaction. I'm doing it as
>> part of my undergraduate research thesis.
>>
>> Using AMBER as the "Low-level" method is standard within similar papers,
>> but my studied cofactor and substrate are not parameterized within
>> Gaussian16's AMBER parameter files.
>>
>> I have seen the Toolset to Assist Oniom calculations (TAO), which would
>> resolve my issue. However it is not compatible with G16.
>>
>> As such, I'd like to ask: How does one manually convert a .frcmod file's
>> contents so it is compatible with Gaussian input (.gjf) using SoftFirst
>> input option?
>
> I hope someone answers here. But you are much more likely to get good
> pointers from Gaussian than from this mailing list.
>
> ....good luck...dac
>
>
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Received on Thu Apr 07 2022 - 11:00:03 PDT
