[lammps-users] NVT to NPH for TIP4P: Out of range

LAMMPS LAMMPS Mailing List Mirror
1

hi, guys,

I ran a water/metal hyrbrid system in use of TIP4P. I applied NPH after unfixing a long time of NVT thermosat.
Got the error: Out of range, cannot compute PPPM. I am just wondering what sort of change NPH imposed to the system to cause this error?

2

The error occurs b/c atoms move too far, too fast.
Are you checking to reneighbor every step if
needed? Does the volume change abruptly?
Have you visualized what happens when you
change to NPH? Have you monitored the thermo
output at a fine timescale when you make the
change?

Steve

3

Steve Plimpton wrote:

The error occurs b/c atoms move too far, too fast.
Are you checking to reneighbor every step if
needed? Does the volume change abruptly?
Have you visualized what happens when you
change to NPH? Have you monitored the thermo
output at a fine timescale when you make the
change?

Steve

hi, guys,

I ran a water/metal hyrbrid system in use of TIP4P. I applied NPH after
unfixing a long time of NVT thermosat.
Got the error: Out of range, cannot compute PPPM. I am just wondering
what sort of change NPH imposed to the system to cause this error?

--
Kind regards,

Percy Song

------------------------------------------------------------------------------
OpenSolaris 2009.06 is a cutting edge operating system for enterprises
looking to deploy the next generation of Solaris that includes the latest
innovations from Sun and the OpenSource community. Download a copy and
enjoy capabilities such as Networking, Storage and Virtualization.
Go to: http://p.sf.net/sfu/opensolaris-get
_______________________________________________
lammps-users mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/lammps-users

Thanks, Steve, I will check what you pointed. Actually the system is well adjusted to target temperature in NVT run and other thermo properties look normal.
I came across the error before in other situation and the 'delay 0 every 1 check yes' is adopted.

For transition between NVE and NVT, there seem no such problems. I don't know whether it's due to some unpredictable abrupt change caused by NPH itself.

4

Can you write a restart file at the timestep ou are changing to NPH,
then when you restart and turn on NPH, it will instantly fail?

If so, that should make it easier to debug.

Steve

5

Thanks, Steve. Yes, the NPH fails instantly when changing to NPH, possibly that the lack of 'elastic force' in TIP4P for liquid phase is hard to maitain a stable pressure instantly?
Otherwise I should go back to debug initial configuration?

Soft potential and nve/limit were all tried for pushing the overlapped configuration. Just hard to get a benchmark to proceed.

Kind regards,

Percy Song

Steve Plimpton wrote:

6

If the cause is that the forces/pressures are huge when
you change to NPH, then you may get a rapid volume
change and lost atoms. Not sure what you mean
by instantly (0th timestep?). If you think it's a LAMMPS
problem rather than a model/physics problem, then you
can post your restart file and restart input script that
fails right away.

Steve