In this paper, we investigate the stability and thermoelectric properties of 1 T PdSSe, PdSTe and PdSeTe Janus structures using density functional theory (DFT). All three systems are narrow gap semiconductors with indirect bandgaps of 0.94 eV, 0.33 eV and 0.34 eV respectively. Compared to transition metal dichalcogenide (TMD) monolayers, PdS 2 and PdSe 2 are semiconductors with wider indirect bandgaps of 1.29 eV and 0.69 eV respectively. Phonon dispersion calculations demonstrate that all pristine and Janus structures are mechanically stable despite the presence of negligible negative frequencies around the Γ point in PdSTe and PdSeTe. Inspection of the lattice thermal conductivity (κ L ) shows that these structures are slightly anisotropic in the x and y directions except for PdSe 2 which shows a higher degree of anisotropy. Influenced by the values of κ L , the thermal electronic conductivity (κ e ), the electronic conductivity (σ) and the Seebeck effect (S), the figure of merit along the x (ZT xx )and y (ZT yy ) directions register the largest values in the case of electron doping for the PdSe 2 and PdSeTe 2D crystals. Interestingly, the figures of merit of the Janus structures are larger than their corresponding pristine PdX 2 (X = S, Se) structures. Once synthesized, such information is crucial for the implementation of the PdXY (Y = Se, Te) structures in industrial applications.

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Coulomb coupling between the two holes in the fullerene cation C 60 2+ results in high-and low-spin terms.Vibronic coupling of the high-spin terms to a single mode of vibration of h g symmetry can distort the lowest adiabatic potential-energy surface into wells of D 3d , D 5d , D 2h , or C 2h symmetry depending upon the precise nature of the coupling produced by different admixtures of the two sets of coupling coefficients arising from the two H-type irreducible representations appearing in the symmetric part of the H H Kronecker product. The symmetry of dynamic distortions of C 60 2+ ions when coupling to all eight of the possible h g modes is takeninto account depends very closely on both the vibronic coupling parameters and the splittings between different Coulomb terms. Using estimates for these parameters from the literature leads us to conclude that the distortional symmetry is most likely to be D 2h , but there is also the possibility that it could be D 3d .

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