High Throughput Screening of Ternary Nitrides with Convolutional Neural Networks

The development of new materials is a core aspect of advancement in synthesis and application for industry. There is a vast number of possible chemical permutations of the basic elements that can be explored to synthesize materials that possess attractive catalytic, mechanical and electrical properties that may not be easily accessible to traditional experimental methods for various reasons, including cost and time considerations. Nitrides, as examples, require very stringent and precise conditions to successfully synthesize making their experimental exploration very slow. In this paper, we employ the use of machine learning algorithms to predict the bulk properties of Ternary Metal Nitrides (TMN), specifically their bulk modulus which is correlated with the hardness of the material. We were able to develop a consistent model with encouraging accuracy, that was able to predict the bulk moduli of materials that previously did not have computed values. The model was trained on $10^3$ ternary materials with known elastic properties and defined structures, and was able to predict the bulk modulus of $\thickapprox 1,000$ Ternary Metal Nitrides (TMNs) to $\thickapprox 80\%$ accuracy. This approach is orders of magnitude faster than the traditional computational approaches like density functional theory (DFT)\cite{dft-paper} which makes exploratory identification of materials with promising properties fast. We propose that such models be used to select interesting candidates for high throughput computation from first principles.Comment: 5 Pages, 5 Figures, 1 Tabl

The Impact of Colonial Land Tenure Policies on the Gusii People in Kenya

Different scholars have looked at the general economic impacts of the land reforms and legal implications at national level. However, a few studies have been done on economic history in Gusiiland. This study aimed at analyzing the impact of the colonial land tenure reforms on the Abagusii customary land tenure practices in Gusii, Kenya. This study used the articulation of modes of production theory to analyze the effects of land reforms on the Abagusii community from 1895 to 1963. Descriptive Survey Design was used to guide the study.Purposive and snowball sampling methods was instrumental in selected the respondents with a sample size of 61 informants. The primary sources of data were obtained from the archives, field interviews, observation and focus group discussions while secondary data was obtained from written sources like books, Journals, magazines, periodicals, Newspaper Articles, unpublished theses, seminar papers, and electronically stored information on the internet. Logical historical method was employed in the actual process of analyzing and interpreting the data gathered.The study established that land consolidation and the issuance of individual land owners with title deeds has increased land conflicts, land titling and issuance of individual titles has increased land speculation, and land tenure reforms have failed to solve land problems or improve the agricultural sector, as well as, failing to change the African mind set or behavior of the smallholder farmers in Gusii, Kenya

Electronic and optical properties of doped TiO2 by many-body perturbation theory

Doping is one of the most common strategies for improving the photocatalytic and solar energy conversion properties of TiO2, hence an accurate theoretical description of the electronic and optical properties of doped TiO2 is of both scientific and practical interest. In this work we use many-body perturbation theory techniques to investigate two typical n-type dopants, niobium and hydrogen, in TiO2 rutile. Using the GW approximation to determine band edges and defect energy levels, and the Bethe-Salpeter equation for the calculation of the absorption spectra, we find that the defect energy levels form nondispersive bands lying 3c2.2 eV above the top of the corresponding valence bands ( 3c0.9 eV below the conduction bands of the pristine material). The defect states are also responsible for the appearance of low-energy absorption peaks that enhance the solar spectrum absorption of rutile. The spatial distributions of the excitonic wave functions associated with these low-energy excitations are very different for the two dopants, suggesting a larger mobility of photoexcited electrons in Nb-TiO2

Many-body perturbation theory calculations using the yambo code

International audienceyambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as quantum-espresso and abinit. yambo's capabilities include the calculation of linear response quantities (both independent-particle and including electron-hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron-phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools

Many-body perturbation theory calculations using the yambo code

yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo's capabilities include the calculation of linear response quantities (both independent-particle and including electron–hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron–phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools