No abstract

Considering the rapid development of experimental techniques for fabricating 2D materials in recent years, various monolayers are expected to be experimentally realized in the near future.Motivated by the recent research activities focused on the honeycomb arsenene monolayers, stability and carrier mobility of non-honeycomb and porous allotropic arsenene are determined using first principles calculations. In addition to five honeycomb structures of arsenene, a total of eight other structures are considered in this study. An extensive analysis comprising energetics, phonon spectra and mechanical properties confirms that these structures are energetically and dynamically stable. All these structures are semiconductors with a broad range of band gap varying from ~1 eV to ~2.5 eV. Significantly, these monolayer allotropes possess anisotropic carrier mobilities as high as several hundred cm 2 V -1 s -1 which is comparable with the well-known 2D materials such as black phosphorene and monolayer MoS2. Combining such broad band gaps and superior carrier mobilities, these monolayer allotropes can be promising candidates for the superior performance of the next generation nanoscale devices. We further explore these monolayer allotropes for photocatalytic water splitting and find that arsenene monolayers have potential for usage as visible light driven photocatalytic water splitting.

By employing the state-of-the-art density functional theory method, we demonstrate that Janus WSeTe monolayer exhibits promising photocatalytic properties for solar water splitting. The results show that the monolayer possesses thermodynamic stability, suitable bandgap (∼1.89 eV), low excitons binding energy (∼0.19 eV) together with high hole mobility (∼103 cm2 V−1 s−1). Notably, the results suggest that the oxygen evolution reaction can undergo spontaneously without any sacrificial reagents. In contrast, the overpotential of hydrogen evolution reaction can partially be overcome by the external potential under solar light irradiation. Furthermore, the intrinsic electric field induced by the symmetry breaking along the perpendicular direction of Janus WSeTe monolayer not only suppresses the electron–hole recombination but also contributes to the solar-to-hydrogen efficiency, which is calculated to be ∼19%. These characteristics make the Janus WSeTe monolayer to be a promising candidate for solar water splitting.

By employing density functional theory, we have explored the stability and electronic and mechanical properties of chalcogen (Se and Te) monolayers.

Linear and polynomial regression model has been used to investigate the COVID-19 outbreak in India and its different states using time series epidemiological data up to 26th May 2020. The data driven analysis shows that the case fatality rate (CFR) for India (3.14% with 95% confidence interval of 3.12% to 3.16%) is half of the global fatality rate, while higher than the CFR of the immediate neighbors i.e. Bangladesh, Pakistan and Sri Lanka. Among Indian states, CFR of West Bengal (8.70%, CI: 8.21-9.18%) and Gujrat (6.05%, CI: 4.90-7.19%) is estimated to be higher than national rate, whereas CFR of Bihar, Odisha and Tamil Nadu is less than 1%. The polynomial regression model for India and its different states is trained with data from 21st March 2020 to 19th May 2020 (60 days). The performance of the model is estimated using test data of 7 days from 20th May 2020 to 26th May 2020 by calculating RMSE and % error. The model is then used to predict number of patients in India and its different states up to 16th June 2020 (21 days). Based on the polynomial regression analysis, Maharashtra, Gujrat, Delhi and Tamil Nadu are continue to remain most affected states in India.