[gmx-users] gas phase force field

[V.V.Chaban]

OPLS is a good choice to start with




On Tue, Jun 23, 2015 at 1:45 AM, Swapnil Kate
<swapnilkate at rocketmail.com> wrote:
> hello,
>
> Thanks for yours valuable comments,
> So Which force fields do you people recommend to simulate gas phase systems?
> Can we simulate gas and liquid mixtures in one go?
>
> Regards
> Swapnil
>
>
>
> On Monday, 22 June 2015 6:26 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>
>
>
>
> On 6/22/15 8:47 AM, V.V.Chaban wrote:
>> Not all organics is polar, Justin. :-)
>>
>
> Obviously.
>
>> Hydrogen bond length, and hence, energy are well limited by sigma in
>> LJ. Even if dipole moments are overestimated by 20%, this should not
>> lead to a proportional increase in the hydrogen bond strength.
>>
>
> Actually, it can and does.  I used a specific example that we know quite
> well.
> Overestimation of dipole moments in vicinal alcohols depresses the gas-phase
> energy leading to incorrect dHvap.  This is a trend in additive force
> fields,
> and we consistently see failures of additive models to respond to different
> conditions as we develop our polarizable force fields (which correctly
> reproduce
> both gas and liquid phase properties).  Most force fields are geared towards
> condensed phase properties.  Of course not all models reflect the same
> properties, but one needs to carefully evaluate the proper behavior in the
> gas
> phase based on available data.  Additive models are generally incapable of
> responding to both gas and liquid states.
>
> -Justin
>
>>
>>
>>
>>
>> On Sun, Jun 21, 2015 at 9:52 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>>>
>>>
>>> On 6/21/15 9:07 AM, V.V.Chaban wrote:
>>>>
>>>> Actually, any existing field, since all of them -- to this or that
>>>> extent -- were cteated under cluster-in-vacuum' approach.
>>>>
>>>
>>> While most biomolecular force fields have their origins in gas-phase QM,
>>> most ultimately target condensed-phase properties.  Additive force fields
>>> thus must overestimate gas-phase dipole moments on the order of ~20% or
>>> more
>>> to capture proper liquid-phase properties.  This is a reason why one will
>>> see overly strong intramolecular hydrogen bonding in polyols, etc.
>>>
>>> -Justin
>>>
>>>>
>>>>
>>>> On Sun, Jun 21, 2015 at 3:02 AM, Swapnil Kate
>>>> <swapnilkate at rocketmail.com> wrote:
>>>>>
>>>>> Hello all,
>>>>> Can any one please tell me which force fields are used for accurate
>>>>> prediction of gas phases on organics?
>>>>> RegardsSwapnil
>>>>>
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>>> --
>>> ==================================================
>>>
>>> Justin A. Lemkul, Ph.D.
>>> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>>>
>>> Department of Pharmaceutical Sciences
>>> School of Pharmacy
>>> Health Sciences Facility II, Room 629
>>> University of Maryland, Baltimore
>>> 20 Penn St.
>>> Baltimore, MD 21201
>>>
>>> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
>>> http://mackerell.umaryland.edu/~jalemkul
>
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> --
> ==================================================
>
> Justin A. Lemkul, Ph.D.
> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>
> Department of Pharmaceutical Sciences
> School of Pharmacy
> Health Sciences Facility II, Room 629
> University of Maryland, Baltimore
> 20 Penn St.
> Baltimore, MD 21201
>
> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
> http://mackerell.umaryland.edu/~jalemkul
>
> ==================================================
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