temperature suddenly drops zero


I am running an input with hybrid potential including two different comb potentials with coulomb potential for the rest of the system. Temperature starts with 300K and should slowly increase to 310K with damping parameter 0.0001. I am using NVT. It has been run for 4000 steps with thermo 50 and with alternatively 40000steps againg thermo 50. Different time steps are evaluated. In the begining temperature starts with 300 and smoothly evaluates to 310 and even for the smallest timestep values in the first few step temperature does not increase or decrease excessively which is good. However a few steps later temperature suddenly drops zero and for the rest of the calculation remains zero. I will ask firstly can I use two different comb potentials? In the comb potential there are 3(Ti-Si-O) different atoms and one type of atom(“O”) is shared for both of the comb potentials. Secondly why temperature drops zero?

Mehmet KO�, MS
Micro and Nano Technology Department
Middle East Technical University

Not enough info to tell you why atoms are freezing. Try visualizing
the system, try dumping the velocities. Are you monitoring the temp
of the entire system?


Hi Mehmet,

If Si and Ti do not interact in your system, it is fine to use them
together. But if they are intended to interact, whether in metal or
oxide form, since there are no Si-Ti parameters defined, Si and Ti
will not interact with each other.