[gmx-users] (no subject)

[Justin Lemkul]

Please keep the discussion on the gmx-users list.

On 6/18/14, 9:10 AM, Amninder wrote:
> My mistake for subtraction but still too far from expt Value. I am using OPLS force field and parameters from virtual chemistry.org and used conditions corresponding to their paper.
>

Post your .mdp files and perhaps we can spot anything that may not be correct.

-Justin

>
>
> Sent from my iPhone
>
> On 18-Jun-2014, at 9:50 PM, Justin Lemkul <jalemkul at vt.edu> wrote:
>
>>
>>
>> On 6/18/14, 1:04 AM, AMNINDER SINGH wrote:
>>> Dear
>>> People,
>>>
>>> I am  trying to calculate enthalpy of vaporization
>>> of methanol.
>>> Using energy
>>> –nmol on equilibrated methanol, E pot comes -5.005 KJ/mol.
>>> Then for EPot
>>> (gas) I got 14.405 KJ/mol.
>>>
>>> Using DHvap
>>> = Epot(gas) - Epot (liquid)+RT.
>>>
>>> My value
>>> comes around 11 KJ/mol much less than experimental value 37.43.
>>>
>>> Any idea
>>> where is mistake might be.
>>
>> It looks like the subtraction you did was incorrect, so your result ends up being about 22 kJ/mol, assuming T = 298 K (RT = 2.478).  Is your force field model expected to reproduce the enthalpy of vaporization?  Where did you get the parameters?
>>
>> -Justin
>>
>> --
>> ==================================================
>>
>> Justin A. Lemkul, Ph.D.
>> Ruth L. Kirschstein NRSA Postdoctoral Fellow
>>
>> Department of Pharmaceutical Sciences
>> School of Pharmacy
>> Health Sciences Facility II, Room 601
>> University of Maryland, Baltimore
>> 20 Penn St.
>> Baltimore, MD 21201
>>
>> jalemkul at outerbanks.umaryland.edu | (410) 706-7441
>> http://mackerell.umaryland.edu/~jalemkul
>>
>> ==================================================

-- 
==================================================

Justin A. Lemkul, Ph.D.
Ruth L. Kirschstein NRSA Postdoctoral Fellow

Department of Pharmaceutical Sciences
School of Pharmacy
Health Sciences Facility II, Room 601
University of Maryland, Baltimore
20 Penn St.
Baltimore, MD 21201

jalemkul at outerbanks.umaryland.edu | (410) 706-7441
http://mackerell.umaryland.edu/~jalemkul

==================================================