Effect of strain on the thermodynamic stability of monolayer MoSe₂, WSe₂ and MoSe₂/WSe₂ heterostructure

Abstract Based on density functional perturbation theory (DFPT), the phonon dispersion of monolayer MoSe 2 , monolayer WSe 2 , and MoSe 2 /WSe 2 heterostructures under biaxial strain were systematically calculated and analyzed, and the maximum strain tolerance of these three structures was investigated. The results reveal that monolayer MoSe 2 and WSe 2 can sustain biaxial tensile strains reaching 18%, while the MoSe 2 /WSe 2 heterostructure can sustain biaxial tensile strains reaching 16%. Furthermore, the effects of biaxial strain on the entropy, enthalpy, free energy, and heat capacity of the three structures were computed. At a fixed temperature, as the applied strain increases, both the entropy and enthalpy of the system exhibit a significant upward trend, whereas the free energy and heat capacity decrease. Notably, temperature has a negligible impact on the heat capacity beyond 300 K. When the thermal performance curves deviate from their regular patterns with increasing strain, the structure becomes damaged and loses stability. These findings provide critical insights into the strain-dependent thermal properties and mechanical limits of monolayer and heterostructure systems.