Hi,
I am simulating diffusion at a given temperature between two binary metallic liquids of different composition. I need to begin the simulation at 2700k with a perfect composition profile, i.e liquid one side of the interface has 0% solute, and liquid on the other side has a uniform distribution of solute.
I have equilibrated both sides of the interface to 2700k separately (to stop any diffusion below this temperature), thus finding equilibrium volume at this temp. I then manually combined the xyz co-ordinates and vx vy vz velocities, into a data file.
Reading this data file, using an nvt, npt or nve ensemble gives initial conditions (timestep 0) that are just what I am looking for. T=2700k, with two liquid structures either side of an interface. But after one timestep (0.001ps) the temperature raises to ~4,000K and before 0.1 ps it is around 60,000K! The atoms that have the highest velocities that bring up the temperature are equally distributed through the sample, so there I believe that there is no problem with the interface or boundaries (e.g atoms overlapping). But just to check I ran the simulation with gaps at the interfaces, which yielded very similar results.
As there is no velocity input whatsoever (in nve, npt and nvt have a fix at 2700) I have no idea how this huge temperature is being generated. Any help as to why this is happening, or advice on a method of separating atoms, equilibrating them to 2700k and then removing the separation to allow diffusion, would be greatly appreciated.
Best
Jack Shuttleworth