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The paper is aimed to understand the key phonon modes that are responsible for the temperature dependent structural phase transition and negative thermal expansion of Hg2Cl2 compound for the first time with the aid of density functional theory and Born-Oppenheimer on the fly molecular dynamics calculations. The phonon dispersion spectra, phonon density of states and Grüneisen parameters for the body-centered tetragonal and base-centered orthorhombic phases of the compound have been explored in detail. The order parameter associated with the phase transition and its nature has also been reported herewith. We believe that the present study will not only help for futuristic designs of improved functionalized systems with Hg2Cl2 compound but also can augment their applications in thermoelectric conversion systems, fibre-optic communications, thermal expansion compensators and in fuel cells. [ABSTRACT FROM AUTHOR]

This paper shows how terahertz light can drive ultrafast topological phase transitions in monolayer transition metal dichalcogenides (TMDs). The phase transition is induced by the light interaction with both electron and phonon subsystems in the material. The mechanism of such a phase transition is formulated by thermodynamics theory: the Gibbs free energy landscape can be effectively modulated under light, and the relative stability between different (meta‐)stable phases can be switched. This mechanism is applied to TMDs and reversible phase transitions between the topologically trivial 2H and nontrivial 1T′ phases are predicted, providing appropriate light frequency, polarization, and intensity are applied. The large energy barrier on the martensitic transformation path can be significantly reduced, yielding a small energy barrier phase transition with fast kinetics. Compared with other phase transition schemes, light illumination has great advantages, such as its non‐contact nature and easy tunability. The reversible topological phase transition can be applicable in high‐resolution fast data storage and in‐memory computing devices. [ABSTRACT FROM AUTHOR]

The 1T phase of transition metal dichalcogenides (TMDs) is predicted to be an excellent anode material of lithium batteries (LIBs) by many previous theoretical investigations, especially in Mo- and W-TMDs, mainly because of its metallic character. However, the Peierls instability will induce a spontaneous transition from 1T to 1T′ phase, which was ignored by previous studies but should play an important role during the cycling process of LIBs. In this paper, the density functional theory calculations were adopted to systematically studied Li diffusion behavior on the different variants of low symmetry 1T′-MoS 2. It was revealed that the diffusion barrier parallel to the Mo-Mo dimerization zigzag chain is almost two times to the perpendicular direction. Besides, the diffusion direction will be turned to ∼120° after Li crosses the domain boundary in a 1T′ multi-domain nanosheet. Similar results could also be observed in Na and K diffusion. Our finding not only revealed the Li (Na or K) diffusion behavior of 1T′-MoS 2 but also propose to control the atom diffusion direction through strain engineering, which may inspire the further development of electronic devices. [Display omitted] • The structural anisotropy of 1T′-MoS 2 will lead to Li diffusion anisotropy. • The diffusion barrier along the Mo-Mo dimerization zig-zag chain is two times than that along the perpendicular direction. • The diffusion direction of Li atoms would be changed in different variants. • Local strain could be applied to control the local variant in a multi-domain nanosheet and then modulate the diffusion direction. [ABSTRACT FROM AUTHOR]

The IrTe transition metal dichalcogenide undergoes a series of structural and electronic phase transitions when doped with Pt. The nature of each phase and the mechanism of the phase transitions have attracted much attention. In this paper, we report scanning tunneling microscopy and spectroscopy studies of Pt-doped IrTe with varied Pt contents. In pure IrTe, we find that the ground state has a 1/6 superstructure, and the electronic structure is inconsistent with Fermi surface nesting-induced charge density wave order. Upon Pt doping, the crystal structure changes to a 1/5 superstructure and then to a quasi-periodic hexagonal phase. First-principles calculations show that the superstructures and electronic structures are determined by the global chemical strain and local impurity states that can be tuned systematically by Pt doping. [ABSTRACT FROM AUTHOR]