Re: How to get the right density of a methane system

From: Monika Madhavi (monikamadhavi_at_gmail.com)
Date: Fri Aug 25 2017 - 03:29:17 CDT

Hi Francesco,

Thanks for the suggestion. Actually the force field you suggested gave good
results. The densities were closer to the experimental values. But I could
not successfully equillibriate the temperatures above 100 K. The system
equillibrates at a total positive energy at the end of the equilibrium.

Thank you.
Best,
Monika

On Sat, Aug 12, 2017 at 11:37 AM, Francesco Pietra <chiendarret_at_gmail.com>
wrote:

> Hi Monika:
> Have a look at
>
> F. Pietra “On Dioxygen and Substrate Access to Soluble Methane
> Monooxygenases. An all-Atom Molecular Dynamics Investigation in Water
> Solution.” Chemistry&Biodiversity, *2016*, e1600158 DOI:
> 10.1002/cbdv.201600158.
>
>
> There you will find very good CHARMM parameters for methane, albeit not
> tried for the liquid state
> fp
>
> On Sat, Aug 12, 2017 at 4:56 AM, Monika Madhavi <monikamadhavi_at_gmail.com>
> wrote:
>
>> Dear all,
>>
>> I want to simulate a system of liquid methane at 91 K and 1 atm. I used
>> some opls parameters from literature and converted them to CHARMM and used
>> for my simulation. Initially I heated the system in NVT and then performed
>> NPT. The system equillibriates but the density of methane after
>> equillibration is higher than the experimental values. What could be the
>> problem, the force field? or are there any special techniques to get the
>> right density of a system. I am using NAMD with CHARMM for my simulations.
>>
>> Thanks in advance.
>> Monika
>>
>> --
>> W.A.Monika Madhavi
>> Lecturer (Probation),
>> Department of Physics,
>> University of Colombo.
>>
>
>

-- 
W.A.Monika Madhavi
Lecturer (Probation),
Department of Physics,
University of Colombo.

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