where m i and v i are the mass and velocities of a particle i within the bin and N f is the total number of degrees of freedom in the bin. Since the force fields used in this investigation were fully flexible, N f = 3N b , where N b was the number of atoms in each bin. The temperature profile was calculated every 0.5 ps and averaged across the whole simulation. ∇T , was calculated by fitting the temperature profile in the linear regions between the hot and cold thermostats. The heat flux was then calculated according to the equation: