Effect of special_bonds on viscosity of SPC/E water using GK method

Dear all,

I have simulated the viscosity of SPC/E water using GK method recently. But a problem just disturbed me for a long time. The simulated values are about 0.3 mPa·s (about 0.7mPa·s in open literatures) at 300K under NVT ensemble when using the default settings of special_bonds. However, when I only changed the special_bonds settings to lj/coul 0.0 0.0 0.5, the simulated viscosities of SPC/E water at different temperatures agree well with that from literatures. I think this is unreasonable because there are no 1-4 interactions in water molecules. So I simulated using different lammps versions but similar results were obtained. I don’t know what the reason is. Can you give me some suggestions? My input file and some results has been shown in attachments. The autocorrelation function using default settings is depicted in blue line while the other condition is depicted in red line.

Best regards,

Tingting Chen

vgk.in (2.63 KB)


You’re saying your simulation results change when you
only change the 1-4 setting for the special_bonds commands,
yet you have a system with no 1-4 interactions?

If that is the case (can’t imagine how), please post
a simple, short input script/data file that runs for
a few time steps and shows different thermo output.