AMBER Archive (2003)

Subject: RE: question on EWALD

From: Sichun Yang (syang_at_physics.ucsd.edu)
Date: Mon Feb 17 2003 - 16:12:42 CST

Thank you for your answer.

>
> You probably have stated this before, but I did not catch it. Anyhow,
> how long has your system been stable at 500K under NPT?

It is about 10 ps.

> I gather you are using TIP3P or SPC/E type solvent. In either case, the
> system can be relatively unstable because TIP3P vaporizes at roughly
> round 400K. If that is the case, you probably should see systematic
> increase in the volume (not the pressure, which is under control). If

I checked it and there are a increasing in the Volume.

> you intend to simulate solution phase, it may be a good idea to use NVT
> instead. The trick is that you may need to "equilibrate" the system at a
> lower temperature using NPT (to maintain reasonable density). You will
> then switch to NVT at 500K.

I need to make it clear for myself. Do you mean using NPT to get a proper
density instead of NVT? And what is the physics behind?

Thanks again,
Sichun