  Molybdenum disulfide (MoS$_2$) is a promising candidate for 2D nanoelectronic
devices, that shows a direct band-gap for monolayer structure. In this work we
study the electronic structure of MoS$_2$ upon both compressive and tensile
strains with first-principles density-functional calculations for different
number of layers. The results show that the band-gap can be engineered for
experimentally attainable strains (i.e. $\pm 0.15$). However compressive strain
can result in bucking that can prevent the use of large compressive strain. We
then studied the stability of the compression, calculating the critical strain
that results in the on-set of buckling for free-standing nanoribbons of
different lengths. The results demonstrate that short structures, or few-layer
MoS$_2$, show semi-conductor to metal transition upon compressive strain
without bucking.
