Re: [AMBER] How to Convert gaussian force constant to Gaff?

From: Pengfei Li <ambermailpengfei.gmail.com>
Date: Tue, 20 Mar 2018 08:14:03 -0500

Hi Hector,

Good. Another thing is when you do the angle force constant conversion, unit of the internal angle force constant in the Gaussian output file is Hartree/(rad^2) while in the GAFF unit of the angle force constant is kcal/(mol*rad^2), again an additional factor of 0.5 needs to be considered.

Kind regards,
Pengfei

> On Mar 19, 2018, at 8:44 PM, Hector A. Baldoni <hbaldoni.unsl.edu.ar> wrote:
>
> Hello !
>
> 1 Hartree*(Bohr^2) = 2240.874995 kcal/(mol*Angstrom^2)
>
> Greeting,
> Hector
>
>
>
>> And an additional factor of 0.5 need to be considered for converting the
>> internal force constant in the Gaussian output file to obtain the force
>> constant in GAFF. This is because there is no 0.5 in front of the bond
>> force and angle force constants in the AMBER force field formulation (See
>> equation 14.1 in the Page 243 of the AMBER 2017 manual:
>> http://ambermd.org/doc12/Amber17.pdf
>> <http://ambermd.org/doc12/Amber17.pdf>).
>>
>>> On Mar 19, 2018, at 5:43 PM, Pengfei Li <ambermailpengfei.gmail.com>
>>> wrote:
>>>
>>> Hi Baris,
>>>
>>> The unit of the internal force constant in the Gaussian output file is
>>> Hartree*(Bohr^2), while the force constant in GAFF is
>>> kcal/(mol*Angstrom^2). You can calculate the conversion factor by
>>> yourself.
>>>
>>> Hope it helps,
>>> Pengfei
>>>
>>>> On Mar 9, 2018, at 10:02 AM, Bar─▒┼Ÿ Kurt <bariskurt007.gmail.com>
>>>> wrote:
>>>>
>>>>
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>
>
> --------------------------------------
> Dr. Hector A. Baldoni
> Profesor Adjunto (FQByF-UNSL)
> Investigador Adjunto (IMASL-CONICET)
> Area de Quimica General e Inorganica
> Universidad Nacional de San Luis
> Chacabuco 917 (D5700BWS)
> San Luis - Argentina
> hbaldoni at unsl dot edu dot ar
> Tel.:+54-(0)266-4520300 ext. 6157
> --------------------------------------
>
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Received on Tue Mar 20 2018 - 06:30:03 PDT
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