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Re: [lammps-users] nonpriodic boundry condition

# Re: [lammps-users] nonpriodic boundry condition

 From: Hossein Geraili Date: Sun, 1 Oct 2017 21:14:30 +0330

Dear Dr. Axel,
I have this much information from article and there is no more than this almost anywhere.

"To calculate the cohesive energy
density, the average internal energy and molar volume of the
liquid were obtained from the liquid simulation, and the average
internal energy of the ideal gas was obtained by simulating a
single [bmim][PF6] ion pair at the same temperature as the liquid
but at zero pressure (i.e., no periodic boundary conditions)."

could you please help me with this exhausting issue. As you said it makes no sense to control temperature, but I need internal energy(total energy) in this temperature to calculate something else.

Best regards

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On Sun, Oct 1, 2017 at 8:46 PM, Axel Kohlmeyer wrote:

On Sun, Oct 1, 2017 at 12:03 PM, Hossein Geraili wrote:
Dear lammps users,
How can I control the temperature in nonperiodic boundary condition without controlling volume with NVE?

​please note, that there is a significant difference between using fix nve and an NVE ensemble. you *can* achieve an NVE ensemble by using fix nve, but using fix nve does not automatically result in an NVE ensemble. this has been explained on this mailing list many, many times.

besides, fix nve does *NOT* control the volume. ​ in fact, to be compatible with creating an NVE ensemble is *MUST NOT* do *any* manipulations of the system, neither volume nor (kinetic) energy.

​​fix nve is fully compatible with non-periodic boundaries.

I want to calculate density at the ideal gas state, so I need to control temperature, but thermostats have no time integration.

however, you are not making much sense here. using a thermostat for an ideal gas is pointless, since ideal gas particles do not interact; so how could they couple with a reservoir?

​also, there is not such thing as an "ideal gas state". an ideal gas is a well defined thermodynamic entity. there is little value to doing simulations of an ideal gas, since all its properties can be obtained analytically.

besides, what has this all to do with periodic-boundary conditions?

axel.

best regards

--
Hosein Geraili Daronkola
Physical Chemistry,
Department of Chemistry,
Sharif University of Technology.
geraili_hosein@...7110...

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Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

--
Hosein Geraili Daronkola