<br><br><div class="gmail_quote">On 3 August 2011 15:31, Dr. Vitaly V. Chaban <span dir="ltr"><<a href="mailto:vvchaban@gmail.com">vvchaban@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div><div></div><div class="h5">On Wed, Aug 3, 2011 at 3:17 PM, Elisabeth <<a href="mailto:katesedate@gmail.com">katesedate@gmail.com</a>> wrote:<br>
><br>
><br>
> On 2 August 2011 15:29, Dr. Vitaly V. Chaban <<a href="mailto:vvchaban@gmail.com">vvchaban@gmail.com</a>> wrote:<br>
>><br>
>> ><br>
>> > Hello,<br>
>> ><br>
>> > I wanted to know your ideas on calculation of heat of vaporization using<br>
>> > a<br>
>> > single phase run rather than running two separate simulations for liquid<br>
>> > and<br>
>> > gas!<br>
>> ><br>
>> > 1- Two separate simulations for liquid and gas<br>
>> ><br>
>> > DHvap = <Ugas> - <Uliq> + RT<br>
>> ><br>
>> > 1a: <total liquid potential> - <*total* potential of a single chain in<br>
>> > vacu<br>
>> >> ( bond+angle+torsion + nonbonded interaction of chain with itself)<br>
>> ><br>
>> > or<br>
>> ><br>
>> > 1b: *<total liquid potential> - < intra potential of a single chain in<br>
>> > vacu<br>
>> >> ( bond+angle+torsion) *<br>
>> ><br>
>> > 2- Single liquid phase run: (non need to run in vacu)<br>
>> ><br>
>> > 2a : DHvap = <total liquid potential> - < intra molecular potential<br>
>> > terms in<br>
>> > liquid phase> (same liquid phase simulation by adding up<br>
>> > bond+angle+torsion<br>
>> > terms)<br>
>> ><br>
>> > 2a: In other worlds *DHvap= <Uliq-nonbonded (vdw+electrostatics)> *<br>
>> ><br>
>> > In my case the latter definition is giving much more accurate results<br>
>> > than<br>
>> > 1a.<br>
>> ><br>
>> > I would like to know your idea and comments on methods 1b and 2a.<br>
>> ><br>
>> > Appreciate your comments.<br>
>> ><br>
>><br>
>> What is your system?<br>
>><br>
> system is liquid hydrocarbon polymer and 1a is giving inaccurate values. 2a<br>
> works far better but it seems not to be a common method.<br>
<br>
<br>
</div></div>First of all, you should understand which particles exist in the vapor<br>
phase of your polymer. Notwithstanding the atomistic simulation. If<br>
this question is answered correctly, any method will provide you a<br>
decent result.<br>
<br>
I don't think that the whole "chains" of this polymer are flying in<br>
the vapor phase.....<br></blockquote><div><br>Hello,<br><br>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. </div><br>Best,<br>
</div><br>