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_-- From owner-chemistry@ccl.net Tue Nov 15 17:01:00 2011 From: "=?utf-8?B?U3rFkXJpIE1pbMOhbg==?= milan,,jgypk.u-szeged.hu" To: CCL Subject: CCL: GCMC isotherms Message-Id: <-45885-111115165850-9220-D4z/dw1pa13hMvD2mSeCAA:+:server.ccl.net> X-Original-From: =?utf-8?B?U3rFkXJpIE1pbMOhbg==?= Content-Type: multipart/alternative; boundary="----=_NextPart_000_0128_01CCA3EA.2E494410" Date: Tue, 15 Nov 2011 22:59:08 +0100 MIME-Version: 1.0 Sent to CCL by: =?utf-8?B?U3rFkXJpIE1pbMOhbg==?= [milan---jgypk.u-szeged.hu] Ez egy tvbbriszes |zenet MIME-formatumban. ------=_NextPart_000_0128_01CCA3EA.2E494410 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Hi Diego, I can recommend to use Mezei=E2=80=99s MMC code = (http://inka.mssm.edu/~mezei/mmc/). In GCMC, the chemical potential, = volume and temperature are constant and relative pressure (i.e. the = pressure of the vapour phase normalized by the pressure of the saturated = vapour) can be given by the actual chemical potential and the chemical = potential corresponding to the point of condensation. In order to get = adsorption isotherm (and find the point of condensation) you should run = a series of simulations varying the chemical potentials systematically = (pay attention for hysteresis in the case of microporous material). To = do the math, all the necessary formula can be found in = Phys.Chem.Chem.Phys., 2010, 12, 4604=E2=80=934616. Good luck!=20 Mil=C3=A1n > From: Alavi, Saman Saman.Alavi^^nrc-cnrc.gc.ca=20 Sent: Tuesday, November 15, 2011 9:13 PM To: Szori, Milan =20 Subject: CCL: GCMC isotherms 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 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 = conditions where the pressure of the gas deviates significantly from the = idea gas prediction, additional calculations will be required to = calculate deviation 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, calculate the fugacity and from that the = chemical potential. This calculation would have to be repeated for each = pressure of the isotherm because the deviation from ideality depends on = the pressure and temperature.=20 Hope this helps! Saman=20 -------------------------------------------------------------------------= ------- > From: owner-chemistry+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 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 gas in a microporous material employing a particular force field (FF) = derived from QM calculations. To perform the simulations, I'm testing GULP and Towhee. (Any other = suggestion for an open source software would be nice!) With 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 question. i. =C2=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 know if (and to skip the format of the FF for Towhee) :=20 ii. =C2=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=C3=B3mez ------=_NextPart_000_0128_01CCA3EA.2E494410 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

Hi Diego,

I can recommend to use Mezei=E2=80=99s MMC code (http://inka.mssm.edu/~mezei/mmc/). = In GCMC,=20 the chemical potential, volume and temperature are constant and relative = pressure (i.e. the pressure of the vapour phase normalized by the = pressure of=20 the saturated vapour) can be given by the actual chemical potential and = the=20 chemical potential corresponding to the point of condensation. In order = to get=20 adsorption isotherm (and find the point of condensation) you should run = a series=20 of simulations varying the chemical potentials systematically (pay = attention for=20 hysteresis in the case of microporous material). To do the math, all the = necessary formula can be found in Phys.Chem.Chem.Phys., 2010, 12,=20 4604=E2=80=934616.

Good luck!

Mil=C3=A1n

From: Alavi, Saman=20 Saman.Alavi^^nrc-cnrc.gc.ca

Sent: Tuesday, November 15, 2011 9:13 PM

To: Szori, Milan

Subject: CCL: GCMC isotherms

Hello Diego,

As a first approximation, you can assume the = gas is=20 ideal. In this case, the activity / fugacity will be the same as the = pressure=20 and you can use the standard ideal gas relation for the chemical = potential. So=20 at this level of approximation, no addition simulation is=20 necessary.

If you are dealing with adsorption under high = pressure,=20 low temperature conditions where the pressure of the gas deviates = significantly=20 > from the idea gas prediction, additional calculations will be required = to=20 calculate deviation from non-ideality. From these you can then = calculate=20 the fugacity and chemical potential. You would need a NPT MC or = MD=20 calculation to calculate the real gas density at the T and P of = interest, and=20 > from this data, calculate the fugacity and from that the chemical = potential.=20 This calculation would have to be repeated for each pressure of the = isotherm=20 because the deviation from ideality depends on the pressure and=20 temperature.

Hope this helps!

Saman

From:=20 owner-chemistry+saman.alavi=3D=3Dnrc.ca*_*ccl.net=20 [owner-chemistry+saman.alavi=3D=3Dnrc.ca*_*ccl.net] On Behalf Of DIEGOI = GOMEZ=20 darkego21##yahoo.com [owner-chemistry*_*ccl.net]
Sent: = November 15,=20 2011 1:41 PM
To: Alavi, Saman
Subject: CCL: GCMC=20 isotherms

Hello...

I am new=20 in MC simulations, therefore any answer at any level is welcome!!

I want to=20 perform GCMC simulations to compute an adsorption isotherm of a gas in a = microporous material employing a particular force field (FF) derived = > from QM=20 calculations.