1) x comp of added average force per atom (in force units)
                (2) y comp of added average force per atom (in force units)
                (3) z comp of added average force per atom (in force units)
         rescale
                (1) desired T at beginning of run
                (2) desired T at end of run
                (3) check for rescaling every this many timesteps
                (4) T window outside of which velocities will be rescaled
                (5) fractional amount (0.0 to 1.0)