VMD-L Mailing List

From: Joel Subach (mjsubach_at_alumni.ncsu.edu)
Date: Wed Apr 24 2024 - 09:00:23 CDT

Hello Josh thank you for your kind update:).

I had amended the ! MP2 6-31G* TightSCF opt to ! RI-MP2 6-31G* TightSCF opt
autoaux rijcosx towards the Geometry Optimization and Charge Optimization
which sped up the ORCA optimization results which successfully functioned
within Geom Opt and Charge Opt.

I had then modified this same above Basis Set to the below in bold which is
thus far executing via ORCA without error(s) as-of-yet. RI-MP2 6-31G*
TightSCF opt
autoaux rijcosx, ! RI-MP2 def2-SVP/C TightSCF Opt NumFreq and ! RI-MP2
def2-TZVP def2-TZVP/C TightSCF Opt NumFreq PAL8, were generating errors
within ORCA, these three would of supposedly generate hessian output.out
files to then be used within the ffTK Bond and Angle Optimization.

*! RKS PBE0 D3BJ def2-TZVP def2/J Opt Freq TightSCF RIJCOSX # (the "def2/J"
is the auxiliary coulomb fitting basis set)*

Hopefully the above makes sense, my inquiry is if the above in bold and
the other Base Sets I used successfully in ORCA should be changed or do
these base
sets seem satisfactory to you.

Thanks if you know:),
Joel 🚀

On Wed, Apr 24, 2024 at 3:35 PM Vermaas, Josh <vermaasj_at_msu.edu> wrote:

> Hi Joel,
>
> What basis set was successful? The rest of CHARMM36 uses HF/6-31G(d), and
> there are some other assumptions in parameterization that depend on this
> basis set. Like the multiplier by 1.16 between QM and MM energies is
> strictly empirical, and probably won't extend to other basis sets. If you
> are using some semi-empirical method, that probably won't be very
> compatible with the assumptions built into the CHARMM parameterization
> scheme, but if its still the HF method with a bigger basis set, that is
> probably fine.
>
> -Josh
>
> On 4/24/24 07:37, Joel Subach wrote:
>
> ....and the ffTK default ORCA Base Set is: ! MP2 6-31G* TightSCF opt
>
> On Wed, Apr 24, 2024 at 12:07 PM Joel Subach <mjsubach_at_alumni.ncsu.edu>
> wrote:
>
>> Hello VMD Forum,
>>
>> Towards the above topic, I have been executing the ffTK Tutorial
>> suggested QM Base Set, however, upon reaching the QM generated Hessian
>> Output the above base set has generated errors, accordingly I have instead
>> executed an ORCA Forum suggested Base Set which is so far executing
>> successfully.
>>
>> Would ffTK regardless suggest the ffTK Tutorial Base Set if functioning
>> in lieu of other Base sets since the HF/6-31G(d) level of theory is to
>> maintain the consistency with the CHARMM force field?
>>
>> Thanks if you know since if not to the above then I may go back and use
>> the ORCA Tutorial to modify each Base Set accordingly.
>>
>> Best,
>> Joel🚀
>>
>
> --
> Josh Vermaasvermaasj_at_msu.edu
> Assistant Professor, Plant Research Laboratory and Biochemistry and Molecular Biology
> Michigan State Universityvermaaslab.github.io
>
>