From owner-chemistry -x- at -x- ccl.net Tue Nov 15 15:40:01 2011 From: "Alavi, Saman Saman.Alavi^^nrc-cnrc.gc.ca" To: CCL Subject: CCL: GCMC isotherms Message-Id: <-45884-111115151320-2972-lY+UN+v0h1JSF8h7NCmWAA..server.ccl.net> X-Original-From: "Alavi, Saman" Content-Language: en-CA Content-Type: multipart/alternative; boundary="_000_001A8CD833A9894A8AED786976F900240BA27BD501NRCCENMB1nrcc_" Date: Tue, 15 Nov 2011 12:13:07 -0800 MIME-Version: 1.0 Sent to CCL by: "Alavi, Saman" [Saman.Alavi{:}nrc-cnrc.gc.ca] --_000_001A8CD833A9894A8AED786976F900240BA27BD501NRCCENMB1nrcc_ Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Hello Diego, As a first approximation, you can assume the gas is ideal. In this case, th= e activity / fugacity will be the same as the pressure and you can use the = standard ideal gas relation for the chemical potential. So at this level of= approximation, no addition simulation is necessary. If you are dealing with adsorption under high pressure, low temperature con= ditions where the pressure of the gas deviates significantly from the idea = gas prediction, additional calculations will be required to calculate devia= tion from non-ideality. From these you can then calculate the fugacity and = chemical potential. You would need a NPT MC or MD calculation to calculate = the real gas density at the T and P of interest, and from this data, calcul= ate the fugacity and from that the chemical potential. This calculation wou= ld have to be repeated for each pressure of the isotherm because the deviat= ion from ideality depends on the pressure and temperature. Hope this helps! Saman ________________________________ > From: owner-chemistry+saman.alavi=3D=3Dnrc.ca!^!ccl.net [owner-chemistry+sama= n.alavi=3D=3Dnrc.ca!^!ccl.net] On Behalf Of DIEGOI GOMEZ darkego21##yahoo.com= [owner-chemistry!^!ccl.net] Sent: November 15, 2011 1:41 PM To: Alavi, Saman Subject: CCL: GCMC isotherms Hello... I am new in MC simulations, therefore any answer at any level is welcome!! I want to perform GCMC simulations to compute an adsorption isotherm of a g= as in a microporous material employing a particular force field (FF) derive= d from QM calculations. To perform the simulations, I'm testing GULP and Towhee. (Any other suggest= ion for an open source software would be nice!) With GULP you can perform a GCMC simulation easily. However, you need a val= ue for the chemical potential (at a given pressure) and here is my first qu= estion. i. =BFHow to obtain efficiently and accurately the chemical potential value= for a given pressure to start the GCMC calculation? In this regard, it is possible to obtain the chemical potential from a 'NPT= ' MC simulation that I could perform in Towhee. However I would like to kno= w if (and to skip the format of the FF for Towhee) : ii. =BFIt is possible to perform a 'NPT' MC simulation with GULP? Any manual, reference, comment or suggestion is welcome!! Thanks in advance for any reply! Diego G=F3mez --_000_001A8CD833A9894A8AED786976F900240BA27BD501NRCCENMB1nrcc_ Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Hello Diego,
 
As a first approximation, you can assume the gas= is ideal. In this case, the activity / fugacity will be the same as the pr= essure and you can use the standard ideal gas relation for the chemical pot= ential. So at this level of approximation, no addition simulation is necessary.
 
If you are dealing with adsorption under high pr= essure, low temperature conditions where the pressure of the gas deviates s= ignificantly from the idea gas prediction, additional calculations will be = required to calculate deviation from non-ideality. From these you can then calculate the fugacity a= nd chemical potential. You would need a NPT MC or MD calcu= lation to calculate the real gas density at the T and P of intere= st, and from this data, calculate the fugacity and from that the chemical potential. This calculation would have to be repeated fo= r each pressure of the isotherm because the deviation from ideality= depends on the pressure and temperature.
 
Hope this helps!
Saman=  
 
From: owner-chemi= stry+saman.alavi=3D=3Dnrc.ca!^!ccl.net [owner-chemistry+saman.alavi= =3D=3Dnrc.ca!^!ccl.net] On Behalf Of DIEGOI GOMEZ darkego21##yahoo.com [owner= -chemistry!^!ccl.net]
Sent: November 15, 2011 1:41 PM
To: Alavi, Saman
Subject: CCL: GCMC isotherms

Hel= lo...
I a= m new in MC simulations, therefore any answer at any level is welcome!!
I w= ant to perform GCMC simulations to compute an adsorption isotherm of a gas = in a microporous material employing a particular force field (FF) derived f= rom QM calculations.
To = perform the simulations, I'm testing GULP and Towhee. (Any other suggestion= for an open source software would be nice!)
Wit= h GULP you can perform a GCMC simulation easily. However, you need a value = for the chemical potential (at a given pressure) and here is my first quest= ion.
i. = =BFHow to obtain efficiently and accurately the chemical potential value fo= r a given pressure to start the GCMC calculation?
In this regard, it is poss= ible to obtain the chemical potential from a 'NPT' MC simulation that I cou= ld perform in = Towhee. However I would like to know if (and to skip the format of the FF for Towhee)  : 
ii.= =BFIt is possible to perform a 'NPT' MC simulation with GULP?
Any= manual, reference, comment or suggestion is welcome!!
Tha= nks in advance for any reply!
Die= go G=F3mez



--_000_001A8CD833A9894A8AED786976F900240BA27BD501NRCCENMB1nrcc_--