[gmx-users] Viscosity Calculation

[Visco, Daniele]

Dear All,


I have been trying to calculate viscosities of some Ionic Liquids and Deep Eutectic Solvents using the NEMD periodic perturbation method in gromacs, but I get, almost always, negative values for both the viscosity and the 2CosZ*Vel-X term. I have tried changing the acceleration rate, increasing the temperature, increasing the output frequency, reducing the timestep, increasing the total number of steps (up to 15 ns simulations) but still I get these meaningless results.


I really don't understand what the problem is and unfortunately no one in my group has any experience with gromacs. Did anyone have the same problem? Do you have any clue of what the cause might be? Please let me know if you would like to see any of my input files, and I will send them here. Thank you in advance for your help and attention.


Best,

Daniele