VMD-L Mailing List

From: Joel Subach (mjsubach_at_alumni.ncsu.edu)
Date: Thu Apr 25 2024 - 05:42:29 CDT

..meaning also is the RKS Method acceptable considering it is not an MP2
nor HF Method to my understanding? Thanks:)

On Wed, Apr 24, 2024 at 4:00 PM Joel Subach <mjsubach_at_alumni.ncsu.edu>
wrote:

> 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
>>
>>