I tried to use fix langevin along with fix NVE. I get this ERROR: atoms lost. However when i use only fix NPT, I do not see any error.
So I would like know if anyone has used fix langevin to achieve thermal equilibrium in two dimensional system.
Chances are your initial config is not good (atoms too close) or
perhaps you are not applying the Langevin thermostat properly. Did you
check that indeed your random forces only have 2d character?
In addition, note that NVE + Langevin is not identical to NPT. One is
constant V the other one constant P.
Carlos