No abstract

Monolayers of molybdenum disulfide MoS2 are considered to be prospective materials for nanoelectronics and various catalytic processes. Since in certain conditions they undergo 1T ↔ 2H phase transitions, studying these phase changes is an urgent task. We present a DFT research of these transitions to show that they can proceed as a solid-state reaction. Two transition states were discovered with energy barriers 1.03 and 1.40 eV. Sulfur atoms in the transition states are shown to be displaced relative to molybdenum atoms so that a tendency of one structural modification to transform into the other modification is seen. This kind of displacements agrees with electron microscopy data reported earlier. The energy parameters indicate that 1T → 2H reactions are exothermic for both transition states and can possibly proceed in a self-sustained manner when initially activated by some external energy impact.

XeO(4) is a noble gas compound remarkable for its high explosiveness in the crystalline state and spontaneous explosion at melting temperature. Both phenomena are studied by analyzing potential energy surfaces corresponding to elementary dissociation acts. It is shown that a spontaneous explosion of xenon tetroxide can be explained by a phase transition associated with structural T(d) → D(2h) change and be triggered by rearrangement of electron levels due to the Jahn-Teller effect.