  Using large scale molecular dynamics simulations we study the orientational
dynamics of a heated Janus particle which exhibits self-propulsion. The
asymmetry in the microscopic interaction of the colloid with the solvent is
implemented by choosing different wetting parameters for the two halves of the
sphere. Consequently a gradient in temperature is created across the poles of
the sphere due to different interfacial resistance across the solid-fluid
boundary in the two hemispheres. It is this self-created temperature gradient
which leads to a self-propulsion along the direction of the symmetry axis. In
this article, we look at the orientational dynamics of such a system, as well
as the subsequent enhancement of the translational diffusivity at late times.
The orientational correlation of the symmetry axis is measured from the
simulation and provides a direct access to the rotational diffusion constant.
The heating leads to an increase in the rotational diffusivity of the colloid.
We quantify this increase in rotational diffusion against the temperature
difference across the poles of the Janus sphere as well as the average surface
temperature difference from the ambient fluid.We show that later quantification
is better and results in a data collapse for different choices of the
microscopic interaction. The average propulsion velocity is also measured for
different choices of the wetting parameter. The directionality of
self-propulsion changes depending on the microscopic interaction. We show that
whenever the attractive interaction of the colloid with the solvent is switched
off, the phoretic mobility changes sign. Further, the propulsion velocity is
zero for heating below a certain threshold value. Finally, we combine the
measured propulsion velocity and the rotational diffusion time to estimate the
enhancement in the long time diffusion coefficient of the particle.
