On 3 August 2011 15:31, Dr. Vitaly V. Chaban <vvcha...@gmail.com> wrote:
> On Wed, Aug 3, 2011 at 3:17 PM, Elisabeth <katesed...@gmail.com> wrote: > > > > > > On 2 August 2011 15:29, Dr. Vitaly V. Chaban <vvcha...@gmail.com> wrote: > >> > >> > > >> > Hello, > >> > > >> > I wanted to know your ideas on calculation of heat of vaporization > using > >> > a > >> > single phase run rather than running two separate simulations for > liquid > >> > and > >> > gas! > >> > > >> > 1- Two separate simulations for liquid and gas > >> > > >> > DHvap = <Ugas> - <Uliq> + RT > >> > > >> > 1a: <total liquid potential> - <*total* potential of a single chain in > >> > vacu > >> >> ( bond+angle+torsion + nonbonded interaction of chain with itself) > >> > > >> > or > >> > > >> > 1b: *<total liquid potential> - < intra potential of a single chain > in > >> > vacu > >> >> ( bond+angle+torsion) * > >> > > >> > 2- Single liquid phase run: (non need to run in vacu) > >> > > >> > 2a : DHvap = <total liquid potential> - < intra molecular potential > >> > terms in > >> > liquid phase> (same liquid phase simulation by adding up > >> > bond+angle+torsion > >> > terms) > >> > > >> > 2a: In other worlds *DHvap= <Uliq-nonbonded (vdw+electrostatics)> * > >> > > >> > In my case the latter definition is giving much more accurate results > >> > than > >> > 1a. > >> > > >> > I would like to know your idea and comments on methods 1b and 2a. > >> > > >> > Appreciate your comments. > >> > > >> > >> What is your system? > >> > > system is liquid hydrocarbon polymer and 1a is giving inaccurate values. > 2a > > works far better but it seems not to be a common method. > > > First of all, you should understand which particles exist in the vapor > phase of your polymer. Notwithstanding the atomistic simulation. If > this question is answered correctly, any method will provide you a > decent result. > > I don't think that the whole "chains" of this polymer are flying in > the vapor phase..... > Hello, Thanks. I have only one single chain in vauo. pbc = no and cutoff is set to zero for method 1a. Simulation runs for 20 ns and is equilibrated. Best,
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