[lammps-users] whether lammps is appropriate to simulate the non-neutral system ?

Dear all,

I wonder whether lammps is appropriate to simulate the non-neutral system. I had a try on a system containing anions with water molecules. In the Nose NVT simulation, I find the energy and temperature are all normal and the dumped structure looks fine. However, the fluctuations of Pressure seem very large. Any suggestions are appreciated.

The following is the dumped pressure values during the NVT simulation of 500 ps after the pre-equilibrium of 500 ps.
.
Press = -785.1851
Press = -767.1133
Press = 1331.8392
Press = -1917.1731
Press = -1243.3406
Press = -232.4234
Press = 1137.7800
Press = -1928.1117
Press = 606.5631
Press = 3683.6084
Press = -827.4826
Press = 2301.7961
Press = -1834.9862
Press = -1921.6627
Press = 1220.7028
Press = 660.8979
Press = 27.7994
Press = 2098.3327
Press = 2576.7876
Press = -401.6788
Press = 841.8094
Press = -416.7566
Press = 684.5414
Press = 3169.2826
Press = 1732.0648
Press = -766.9916
Press = 1561.2113
Press = 599.7846
Press = -943.5037
Press = -3433.1003
Press = 479.4703
Press = -323.1026
Press = -140.7215
Press = -253.5449
Press = -353.4675
Press = 382.7678
Press = 130.8779
Press = 172.0290
Press = 1402.3883
Press = 2410.0388
Press = -1.4862
Press = 1118.4218
Press = -1362.4432
Press = 2536.3626
Press = 526.4374
Press = 1289.4608
Press = -2657.5879
Press = -437.5048
Press = 414.7711
Press = 2308.7411
Press = 2868.4946

Dear all,

I wonder whether lammps is appropriate to simulate the non-neutral system. I
had a try on a system containing anions with water molecules. In the Nose
NVT simulation, I find the energy and temperature are all normal and the
dumped structure looks fine. However, the fluctuations of Pressure seem very
large. Any suggestions are appreciated.

pressure fluctuations in condensed systems _are_ large,
especially if the system is small. you didn't state how
many water molecules you system contains and at what
density/temperature you are running.

cheers,
   axel.