  Using density functional theory, we explore the possibility of two monolayer
monochalcogenides, namely, MoS and WS (buckled and puckered). Our results on
cohesive energy and phonon dispersion predict that the buckled structures of
both MoS and WS are stable. On the other hand, while the puckered structure of
WS clearly shows a dynamical instability, the same for MoS may have a stable
configuration. Charge analyses predict ionic-like bonding in these systems.
Density of states and band structure reveal a non-magnetic metallic nature for
MoS in the stable configurations. However, for the buckled WS, our study
predicts a non-magnetic semi-metallic nature. Further, semi-metal to indirect
semiconductor transition has been observed for tensile strain of 5%, 6% and 8%.
