No transition state was found for migration from X to either M or H on any of the three monolayers, implying that the relaxed structures for single atom adsorption at site X is not a local energy minimum, but rather a saddle point. To further probe the stability of this structure, vibrational analysis was performed on the relaxed structure for single atom adsorption at X on WS 2 . In doing this two imaginary vibrational modes were found, with frequencies of -22.33 and -29.60 cm -1 . This implies that this structure is a second order saddle point on the potential energy surface, and therefore that this geometry is unstable at finite temperature.