  We study the electronic response of Janus transition metal dihalide (TMH)
nanotubes to mechanical deformations using Kohn-Sham density functional theory.
Specifically, considering twelve armchair and zigzag Janus TMH nanotubes that
are expected to be stable from the phonon analysis of flat monolayer
counterparts, we first compute their equilibrium diameters and then determine
the variation in bandgap and effective mass of charge carriers with the
application of tensile and torsional deformations. We find that the nanotubes
undergo a linear and quadratic decrease in bandgap with tensile and shear
strain, respectively. In addition, there is a continual increase and decrease
in the effective mass of electrons and holes, respectively. We show that for a
given strain, the change in bandgap for the armchair nanotubes can be
correlated with the transition metal's in-plane $d$ orbital's contribution to
the projected density of states at the bottom of the conduction band.
