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We study the charge transfer between colliding ions, atoms, or molecules, within time-dependent density functional theory. Two particular cases are presented, the collision between a proton and a Helium atom, and between a gold atom and a butane molecule. In the first case, proton kinetic energies between 16 keV and 1.2 MeV are considered, with impact parameters between 0.31 and 1.9 Å. The partial transfer of charge is monitored with time. The total cross-section is obtained as a function of the proton kinetic energy. In the second case, we analyze one trajectory and discuss spin-dependent charge transfer between the different fragments. [ABSTRACT FROM AUTHOR]

For satellites in the Low Earth Orbit (LEO) region, the drag coefficient is a primary source of uncertainty for orbit determination and prediction. Researchers at the Los Alamos National Laboratory (LANL) have created the so-called Response Surface Modeling (RSM) toolkit to provide the community with a resource for simulating and modeling satellite drag coefficients for satellites with complex geometries (modeled using triangulated facets) in the free molecular flow (FMF) regime. The toolkit fits an interpolation surface using non-parametric Gaussian Process Regression (GPR) over drag coefficient data computed using the numerical Test Particle Monte Carlo (TPMC) method. The fitted response surface provides a substantial computational benefit over numerical approaches for calculating drag coefficients. In this work, the RSM toolkit is further developed into a versatile software with extended capabilities. The capabilities are specifically expanded to include uncertainty quantification and adaptation for automatic development of regression models for satellites with non-stationary components (e.g. rotating solar panels). Furthermore, the toolkit uses Python 3.x and C programming languages to provide an open source software package with a OSI approved GPL license. To assist the end user, the new RSM toolkit has been developed to have a user-friendly installation process and is provided with extensive documentation. The analysis of two different conceptual satellites is performed during this work: a simple cube and a CubeSat consisting of a simple cube body with 2 rotating solar panels. During the creation of the regression model for each satellite for different atmospheric species, it is found that the cube's minimum Root Mean Squared Error (RMSE) is 0.00211 and the maximum RMSE is 0.00350. The CubeSat has a minimum RMSE of 0.00304 and the maximum is 0.00498. These results are overall conducive of a well performing regression model. [ABSTRACT FROM AUTHOR]

• In AgAl 1−x Fe x O 2 , Fe atoms cluster at small proximities to each other for x ≤ 3%. • In both delafossites, Fe atoms prefer to occupy the same crystallographic plane. • In AgAl 0.98 Fe 0.02 O 2 , Fe-Fe distance affects the broadening of the Fe states. • For x ≥ 3%, majority of the Fe density concentrates at the isolated Fe atom. • Shift in the valence band edge is caused by the Fe states near the Gamma point. Delafossite materials have been studied for a long time for photovoltaic and catalytic applications due to their wide band gaps and bipolar conductivities. These systems have forbidden fundamental band gaps which are much smaller than their apparent optical gaps. Making optical transitions permissible across the fundamental gap allows photocatalytic reactions to harness solar light in the visible region. Recently, it has been shown that B site doping can break the inversion symmetry of these delafossites allowing light absorption across the fundamental gap. We study structural and electronic properties of two Fe-doped delafossites, AgAl 1−x Fe x O 2 and AgGa 1−x Fe x O 2 (x = 1–5%) using high-throughput calculations. Preferable Fe dopant locations in both these systems are studied using two metrics. Based on the electronic density of states and unfolded band structures, we find that Fe impurities mainly affect the valence band edges of both these systems. New Fe states at the Г point can result in lower energy optical transitions compared to the undoped delafossites. The estimated reductions in the direct band gap at the Gamma point are 1.3 eV and 0.5 eV for AgAl 1−x Fe x O 2 and AgGa 1−x Fe x O 2 respectively. Hence, Fe doped silver delafossites are possible candidates to be tested as catalysts under visible light. [ABSTRACT FROM AUTHOR]

First principles calculations have been employed to search for energetically stable structures of the Mg-Li binary system over all possible Mg concentrations. Volume, space group, c/a and b/a ratios, vibrational contribution to the heat capacity, and Debye temperature are reported to investigate the effects of Li concentration on the Mg-Li binary system. Structures of high symmetry and those lying on or close to the convex hull are further explored to search for dynamic and elastic stability. Five ground state structures were found at Li 1 Mg 13 , Li 1 Mg 2 , Li 1 Mg 1 , Li 7 Mg 2 , and Li 15 Mg 1 compositions. Elastic constants and elastic properties of the selected low energy structures were calculated and analyzed. We also investigate the effect of the phonon band gap found in Li 1 Mg 1 and Li 1 Mg 2 on lattice thermal conductivity. [ABSTRACT FROM AUTHOR]