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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Hybrid density functional study of structural and electronic properties of functionalized Ti n + 1 X n ( X = C , N) monolayers
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First-principles study of compensation mechanisms in negatively charged LaGaO 3 /MgAl 2 O 4 interfaces
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Temperature-driven phase transformation in Y 3 Co: Neutron scattering and first-principles studies
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Theoretical study of the ground-state structures and properties of niobium hydrides under pressure,
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First-principles Study of Thermal Transport in FeSb2
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Spin excitations in cubic maghemite nanoparticles studied by time-of-flight neutron spectroscopy
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Correlation between the valence state of cerium and the magnetic transition in Ce(Ru 1-x Fe x ) 2 Al 10 studied by resonant x-ray emission spectroscopy
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First-principles study of high-field-related electronic behavior of group-III nitrides
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Complex magnetic ordering in CeGe 1.76 studied by neutron diffraction
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First-principles multiple-barrier diffusion theory. The case study of interstitial diffusion in CdTe
The diffusion of particles in solid-state materials generally involves several sequential thermal-activation processes. However, presently, diffusion coefficient theory only deals with a single barrier, i.e., it lacks an accurate description to deal with multiple-barrier diffusion. Here, we develop a general diffusion coefficient theory for multiple-barrier diffusion. Using our diffusion theory and first-principles calculated hopping rates for each barrier, we calculate the diffusion coefficients of Cd, Cu, Te, and Cl interstitials in CdTe for their full multiple-barrier diffusion pathways. As a result, we found that the calculated diffusivity agrees well with the experimental measurement, thus justifying our theory, which is general for many other systems.
Pressure-Induced Structural Phase Transition in CeNi: X-ray and Neutron Scattering Studies and First-Principles Calculations
The pressure-induced structural phase transition in the intermediate-valence compound CeNi has been investigated by x-ray and neutron powder diffraction techniques. It is shown that the structure of the pressure-induced CeNi phase (phases) can be described in terms of the Pnma space group. Equations of state for CeNi on both sides of the phase transition are derived and an approximate P-T phase diagram is suggested for P<8 GPa and T<300 K. The observed Cmcm→Pnma structural transition is then analyzed using density functional theory calculations, which successfully reproduce the ground state volume, the phase transition pressure, and the volume collapse associated with the phase transition.
Quantifying electronic correlation strength in a complex oxide: a combined DMFT and ARPES study of LaNiO{sub 3}
The electronic correlation strength is a basic quantity that characterizes the physical properties of materials such as transition metal oxides. Determining correlation strengths requires both precise definitions and a careful comparison between experiment and theory. In this paper, we define the correlation strength via the magnitude of the electron self-energy near the Fermi level. For the case of LaNiO3, we obtain both the experimental and theoretical mass enhancements m/m by considering high resolution angle-resolved photoemission spectroscopy (ARPES) measurements and density functional+dynamical mean field theory (DFT+DMFT) calculations.We use valence-band photoemission data to constrain the free parameters in the theory and demonstrate a quantitative agreement between the experiment and theory when both the realistic crystal structure and strong electronic correlations are taken into account. In addition, by considering DFT+DMFT calculations on epitaxially strained LaNiO3, we find a strain-induced evolution of m/m in qualitative agreement with trends derived from optics experiments. These results provide a benchmark for the accuracy of the DFT+DMFT theoretical approach, and can serve as a test case when considering other complex materials. By establishing the level of accuracy of the theory, this work also will enable better quantitative predictions when engineering new emergent properties in nickelate heterostructures.
Suppression of magnetic order in CaCo 1.86 As 2 with Fe substitution: Magnetization, neutron diffraction, and x-ray diffraction studies of Ca ( Co 1 – x Fe x ) y As 2
Magnetization, neutron diffraction, and high-energy x-ray diffraction results for Sn-flux grown single-crystal samples of Ca(Co 1–x Fe x ) y As 2 , 0 ≤ x ≤ 1, 1.86 ≤ y ≤ 2, are presented and reveal that A-type antiferromagnetic order, with ordered moments lying along the c axis, persists for x ≲ 0.12(1). The antiferromagnetic order is smoothly suppressed with increasing x, with both the ordered moment and Néel temperature linearly decreasing. Stripe-type antiferromagnetic order does not occur for x ≤ 0.25, nor does ferromagnetic order for x up to at least x = 0.104, and a smooth crossover from the collapsed-tetragonal (cT) phase of CaCo 1.86 As 2 to the tetragonal (T) phase of CaFe 2 As 2 occurs. Furthermore, these results suggest that hole doping CaCo 1.86 As 2 has a less dramatic effect on the magnetism and structure than steric effects due to substituting Sr for Ca.