scholarly journals Theoretical investigations of hydrogen absorption in the A15 intermetallics Ti3Sb and Ti3Ir

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gordon J. Miller ◽  
Ranuri S. Dissanayaka Mudiyanselage ◽  
Weiwei Xie
Keyword(s):  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Hydrogen Atoms ◽  
Metal Metal ◽  
Theoretical Investigations ◽  
Densities Of States ◽  
The Difference ◽  
Structure Calculations ◽  
Hydrogen Insertion

Abstract Ti3Sb and Ti3Ir adopt the A15 (Cr3Si type) structure and are reported to incorporate hydrogen atoms to an extent, respectively, of Ti3SbH∼3 and Ti3IrH3.8. First-principles electronic structure calculations were performed to identify factors contributing to the difference in maximum hydrogen composition for these two intermetallic compounds. Relative energies and changes in energy densities of states and crystal orbital Hamilton populations upon H insertion in the intermetallic compounds were examined. In both compounds, hydrogen atoms are attracted to [Ti4] tetrahedral interstitial sites over any others. The natures of metal-hydrogen and metalloid-hydrogen bonding and the effects of hydrogen insertion on metal-metal and metal-metalloid bonding have an influence on the maximum hydrogen contents for Ti3Sb and Ti3Ir.

Stability and Structures of Constitutional Defects in Nonstoichiometric Intermetallic Compounds by First-Principles Calculations

2005 ◽  
Vol 475-479 ◽  
pp. 3111-3114
Author(s):  
Masataka Mizuno ◽  
Hideki Araki ◽  
Yasuharu Shirai
Keyword(s):  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Stoichiometric Composition ◽  
Electronic Structure Calculations ◽  
First Principles Calculations ◽  
Compositional Dependence ◽  
Wide Range ◽  
Formation Energies ◽  
Structure Calculations

Some of intermetallic compounds exist in a wide range of concentration around the stoichiometric composition. First-principles electronic structure calculations have been performed for constitutional defects in non-stoichiometric CoAl and CoTi in order to investigate their stabilities and structural relaxations induced by constitutional defects. For the evaluation of stabilities of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters are obtained by the calculations employing supercells in various sizes. The lattice relaxations around constitutional defects are discussed by analyzing the change in electronic structures induced by constitutional defects.

scholarly journals Table-top extreme ultraviolet second harmonic generation

2021 ◽  
Vol 7 (21) ◽  
pp. eabe2265
Author(s):  
Tobias Helk ◽  
Emma Berger ◽  
Sasawat Jamnuch ◽  
Lars Hoffmann ◽  
Adeline Kabacinski ◽  
...  
Keyword(s):  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
First Principles ◽  
Extreme Ultraviolet ◽  
Second Harmonic ◽  
High Harmonic ◽  
Electronic Structure Calculations ◽  
Free Electron Lasers ◽  
X Ray ◽  
Structure Calculations

The lack of available table-top extreme ultraviolet (XUV) sources with high enough fluxes and coherence properties has limited the availability of nonlinear XUV and x-ray spectroscopies to free-electron lasers (FELs). Here, we demonstrate second harmonic generation (SHG) on a table-top XUV source by observing SHG near the Ti M2,3 edge with a high-harmonic seeded soft x-ray laser. Furthermore, this experiment represents the first SHG experiment in the XUV. First-principles electronic structure calculations suggest the surface specificity and separate the observed signal into its resonant and nonresonant contributions. The realization of XUV-SHG on a table-top source opens up more accessible opportunities for the study of element-specific dynamics in multicomponent systems where surface, interfacial, and bulk-phase asymmetries play a driving role.

Effect of Boron and Hydrogen on the Electronic Structure of Ni3Al

1993 ◽  
Vol 319 ◽  
Author(s):  
N. Kioussis ◽  
H. Watanabe ◽  
R.G. Hemker ◽  
W. Gourdin ◽  
A. Gonis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Charge Density ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Interstitial Region ◽  
Ordered Intermetallic ◽  
Lmto Method ◽  
Structure Calculations

AbstractUsing first-principles electronic structure calculations based on the Linear-Muffin-Tin Orbital (LMTO) method, we have investigated the effects of interstitial boron and hydrogen on the electronic structure of the L12 ordered intermetallic Ni3A1. When it occupies an octahedral interstitial site entirely coordinated by six Ni atoms, we find that boron enhances the charge distribution found in the strongly-bound “pure” Ni3AI crystal: Charge is depleted at Ni and Al sites and enhanced in interstitial region. Substitution of Al atoms for two of the Ni atoms coordinating the boron, however, reduces the interstitial charge density between certain atomic planes. In contrast to boron, hydrogen appears to deplete the interstitial charge, even when fully coordinated by Ni atoms. We suggest that these results are broadly consistent with the notion of boron as a cohesion enhancer and hydrogen as an embrittler.

scholarly journals Spin Polarization Properties of Pentagonal PdSe2 Induced by 3D Transition-Metal Doping: First-Principles Calculations

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2339 ◽  
Author(s):  
Xiuwen Zhao ◽  
Bin Qiu ◽  
Guichao Hu ◽  
Weiwei Yue ◽  
Junfeng Ren ◽  
...  
Keyword(s):  
Transition Metal ◽  
Spin Polarization ◽  
First Principles ◽  
Magnetic Moments ◽  
First Principles Calculations ◽  
Density Distributions ◽  
Metal Atoms ◽  
Transition Metal Atoms ◽  
Theoretical Investigations ◽  
Densities Of States

The electronic structure and spin polarization properties of pentagonal structure PdSe2 doped with transition metal atoms are studied through first- principles calculations. The theoretical investigations show that the band gap of the PdSe2 monolayer decreases after introducing Cr, Mn, Fe and Co dopants. The projected densities of states show that p-d orbital couplings between the transition metal atoms and PdSe2 generate new spin nondegenerate states near the Fermi level which make the system spin polarized. The calculated magnetic moments, spin density distributions and charge transfer of the systems suggest that the spin polarization in Cr-doped PdSe2 will be the biggest. Our work shows that the properties of PdSe2 can be modified by doping transition metal atoms, which provides opportunity for the applications of PdSe2 in electronics and spintronics.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

scholarly journals First principles methods using CASTEP

2005 ◽  
Vol 220 (5/6) ◽  
Author(s):  
Stewart J. Clark ◽  
Matthew D. Segall ◽  
Chris J. Pickard ◽  
Phil J. Hasnip ◽  
Matt I. J. Probert ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Future Development ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Development Plans ◽  
Near Future ◽  
Structure Calculations

AbstractThe CASTEP code for first principles electronic structure calculations will be described. A brief, non-technical overview will be given and some of the features and capabilities highlighted. Some features which are unique to CASTEP will be described and near-future development plans outlined.

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