Initializing velocity

I have a single particle in a box with a reduced temperature (LJ units ) of 1 unit. I keep getting an error whenever I use create velocity command to initialize the velocity. The error says “attempting to rescale a zero temperature” I have tried all possible ways to correct that but to no avail. I specifically want to use just one particle in my box.

Setting a temperature for a single particle makes no sense in statistical mechanical terms.
You can, of course, assign a velocity and thus a kinetic energy to your particle with velocity set.