UC Riverside

The singular density of states and the two Fermi wavevectors resulting from a ring-shaped or "Mexican hat'' valence band give rise to unique trends in the charged impurity scattering rates and charged impurity limited mobilities. Ring shaped valence bands are common features of many monolayer and few-layer two-dimensional materials including the III-VI materials GaS, GaSe, InS, and InSe. The wavevector independence of the screening, calculated within the random phase approximation, is so strong that it is the dominant factor determining the overall trends of the scattering rates and mobilities with respect to temperature and hole density. Charged impurities placed on the substrate and in the 2D channel are considered. The different wavevector dependencies of the bare Coulomb potentials alter the temperature dependence of the mobilities. Moving the charged impurities 5 {\AA} from the center of the channel to the substrate increases the mobility by an order of magnitude by suppressing the large wavevector backscattering within the outer Fermi ring.

Using first-principles calculations, We investigate the cobalt (111) surface as an alternative substrate for the growth of hexagonal boron nitride (h-BN). We find the adsorption energies of B and N to be larger

on the Co(111) surface compared to the commonly used Cu(111) surface. Trace concentrations of carbon within the Co(111) substrate are found to lower the adsorption energies of B and N on Co(111). The most favorable binding sites and the migration barriers between these sites are also elucidated using nudged elastic band calculations.

Despite multiple successful applications of high-throughput computational materials design from first principles, there are a number of factors that inhibit its future adoption. Of particular importance are the limited ability to provide high fidelity in a reliable manner and the limited accessibility to non-expert users. We present example applications of a novel approach, where high-fidelity first-principles simulation techniques, density functional theory with hybrid screened exchange (HSE) and the GW approximation, are standardized and made available online in an accessible and repeatable setting. We apply this approach to extract electronic band gaps and band structures for a diverse set of 847 materials ranging from pure elements to III-V and II-VI compounds, ternary oxides and alloys. We find that for HSE and G0W0, the average relative error fits within 20%, whereas for conventional generalized gradient approximation the error is 55%. For HSE we find the average calculation time on an up-to-date server centrally available from a public cloud provider fits within a 48 hours window. This work provides a cost-effective, accessible and repeatable practical recipe for performing high-fidelity first-principles calculations of electronic materials in a high-throughput manner.