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Using first-principles density functional theory calculations, we investigate the structure, stability, optical modes and electronic band gap of a distorted tetragonal MoS$_2$ monolayer (T-MoS$_2$). Our simulated scanning tunnel microscopy (STM) images of T-MoS$_2$ are dramatically similar with those STM images which were identified as K$_{x}$(H$_{2}$O)$_{y}$MoS$_{2}$ from a previous experimental study. This similarity suggests that T-MoS$_2$ might have already been observed in experiment but was unexpectedly misidentified. Furthermore, we verify the stability of T-MoS$_2$ from thermal, mechanical and dynamic aspects, by emph{ab initio} molecular dynamics simulation, elastic constants evaluation and phonon band structure calculation based on density functional perturbation theory, respectively. In addition, we calculate the eigenfrequencies and eigenvectors of the optical modes of T-MoS$_2$ at $Gamma$ point and distinguish their Raman and infrared activity by pointing out their irreducible representations using group theory; at the same time, we compare the Raman modes of T-MoS$_2$ with those of H-MoS$_2$ and T-MoS$_2$. Our results provide a useful guidance for further experimental identification and characterization of T-MoS$_2$.
Chemically and mechanically exfoliated MoS$_2$ single-layer samples have substantially different properties. While mechanically exfoliated single-layers are mono-phase (1H polytype with Mo in trigonal prismatic coordination), the chemically exfoliate
We measure the thermal time constants of suspended single layer molybdenum disulfide drums by their thermomechanical response to a high-frequency modulated laser. From this measurement the thermal diffusivity of single layer MoS$_2$ is found to be 1.
We present a theoretical study using density functional calculations of the structural, electronic and magnetic properties of 3d transition metal, noble metal and Zn atoms interacting with carbon monovacancies in graphene. We pay special attention to
To date, germanene has only been synthesized on metallic substrates. A metallic substrate is usually detrimental for the two-dimensional Dirac nature of germanene because the important electronic states near the Fermi level of germanene can hybridize
First-principles density functional theory methods are used to investigate the structure, energetics, and vibrational motions of the neutral vacancy defect in diamond. The measured optical absorption spectrum demonstrates that the tetrahedral $T_d$ p