scholarly journals Directional dependency of electronic stopping in nickel, projectile’s excited charge state and momentum transfer

2021 ◽  
Vol 75 (11) ◽  
Author(s):  
Edwin E. Quashie ◽  
Xavier Andrade ◽  
Alfredo A. Correa
Keyword(s):  
Momentum Transfer ◽  
Density Functional ◽  
Reasonable Agreement ◽  
Stopping Power ◽  
Functional Theory ◽  
Ab Initio Simulations ◽  
Light Ions ◽  
Electronic Densities ◽  
First Time ◽  
Electronic Stopping Power

AbstractWe studied the directional dependency of electronic stopping power of swift light ions in nickel using real-time time-dependent density functional theory. We report a variation of electronic stopping for moving ions as the projectile probes different electronic densities of the host material. These results show that while the predicted magnitude stays in reasonable agreement with experiment, for $$v > 2$$ v > 2 . a.u. simulating only low index crystallographic directions is not enough to sample the experimental average values. The ab initio simulations give us access to microscopic quantities, such as non-adiabatic forces, momentum transfer and transient excited state charges of the projectile and host ions, which are not available through other methods. We report these quantities for the first time.

Computational investigation of the valid valence state contribution in calculating the electronic stopping power of a proton in bulk Al within the linear response approach

2020 ◽  
Vol 98 (2) ◽  
pp. 167-171 ◽  
Author(s):  
Abdullah Atef Shukri ◽  
Ahmad Al-Qawasmeh ◽  
M.M. Al Shorman ◽  
A. Alsaad
Keyword(s):  
Linear Response ◽  
Density Functional ◽  
Ion Irradiation ◽  
Correlation Effect ◽  
Stopping Power ◽  
Functional Theory ◽  
Valence States ◽  
Valence Electrons ◽  
Extrapolation Scheme ◽  
Electronic Stopping Power

The electronic stopping power is a fundamental quantity to many technological fields that use ion irradiation. Here we investigate the validity of using a fully ab initio computational scheme based on linear response time-dependent density functional theory to predict the random electronic stopping power (RESP) of a proton in bulk aluminum. We verify the power of using the extrapolation scheme to overcome the expected convergence issue of the RESP calculations. We show that the calculated RESP of valence electrons compares well with experimental data for low proton velocity only when at full convergence and including the exchange-correlation effect. We demonstrate that the inclusion of valence states only is sufficient for calculating the electronic stopping power up to the stopping maximum.

scholarly journals Single-crystalline epitaxial TiO film: A metal and superconductor, similar to Ti metal

2021 ◽  
Vol 7 (2) ◽  
pp. eabd4248
Author(s):  
Fengmiao Li ◽  
Yuting Zou ◽  
Myung-Geun Han ◽  
Kateryna Foyevtsova ◽  
Hyungki Shin ◽  
...  
Keyword(s):  
Transition Metal ◽  
Density Functional ◽  
Tight Binding ◽  
Crystal Form ◽  
Titanium Monoxide ◽  
Binding Model ◽  
Functional Theory ◽  
Single Crystalline ◽  
First Time ◽  
Lattice Matched

Titanium monoxide (TiO), an important member of the rock salt 3d transition-metal monoxides, has not been studied in the stoichiometric single-crystal form. It has been challenging to prepare stoichiometric TiO due to the highly reactive Ti2+. We adapt a closely lattice-matched MgO(001) substrate and report the successful growth of single-crystalline TiO(001) film using molecular beam epitaxy. This enables a first-time study of stoichiometric TiO thin films, showing that TiO is metal but in proximity to Mott insulating state. We observe a transition to the superconducting phase below 0.5 K close to that of Ti metal. Density functional theory (DFT) and a DFT-based tight-binding model demonstrate the extreme importance of direct Ti–Ti bonding in TiO, suggesting that similar superconductivity exists in TiO and Ti metal. Our work introduces the new concept that TiO behaves more similar to its metal counterpart, distinguishing it from other 3d transition-metal monoxides.

Experimental and computational investigations of TiIrB: a new ternary boride with Ti1+x Rh2−x+y Ir3−y B3-type structure

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Jan P. Scheifers ◽  
Kate A. Gibson ◽  
Boniface P. T. Fokwa
Keyword(s):  
Density Functional ◽  
Ternary Phase ◽  
Structure Type ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
Arc Melting ◽  
Ternary Boride ◽  
Charge Analysis ◽  
First Time ◽  
Bader Charge Analysis

Abstract A new ternary phase, TiIrB, was synthesized by arc-melting of the elements and characterized by powder X-ray diffraction. The compound crystallizes in the orthorhombic Ti1+x Rh2−x+y Ir3−y B3 structure type, space group Pbam (no. 55) with the lattice parameters a = 8.655(2), b = 15.020(2), and c = 3.2271(4) Å. Density Functional Theory (DFT) calculations were carried out to understand the electronic structure, including a Bader charge analysis. The charge distribution of TiIrB in the Ti1+x Rh2−x+y Ir3−y B3-type phase has been evaluated for the first time, and the results indicate that more electron density is transferred to the boron atoms in the zigzag B4 units than to isolated boron atoms.

Thermodynamic Properties of CaSiO3 Perovskite at High Pressure and High Temperature

2009 ◽  
Vol 64 (5-6) ◽  
pp. 399-404 ◽  
Author(s):  
Zi-Jiang Liu ◽  
Xiao-Ming Tan ◽  
Yuan Guo ◽  
Xiao-Ping Zheng ◽  
Wen-Zhao Wu
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Harmonic Approximation ◽  
Debye Model ◽  
Functional Theory ◽  
Casio3 Perovskite ◽  
First Time

The thermodynamic properties of tetragonal CaSiO3 perovskite are predicted at high pressures and temperatures using the Debye model for the first time. This model combines the ab initio calculations within local density approximation using pseudopotentials and a plane wave basis in the framework of density functional theory, and it takes into account the phononic effects within the quasi-harmonic approximation. It is found that the calculated equation of state is in excellent agreement with the observed values at ambient condition. Based on the first-principles study and the Debye model, the thermal properties including the Debye temperature, the heat capacity, the thermal expansion and the entropy are obtained in the whole pressure range from 0 to 150 GPa and temperature range from 0 to 2000 K.

scholarly journals Local and electronic structure around Ga in CdTe: evidence of DX- and A-centers

2012 ◽  
Vol 20 (1) ◽  
pp. 166-171
Author(s):  
Vasil Koteski ◽  
Jelena Belošević-Čavor ◽  
Petro Fochuk ◽  
Heinz-Eberhard Mahnke
Keyword(s):  
Density Functional ◽  
Plane Waves ◽  
Lattice Relaxation ◽  
Defect Structures ◽  
Functional Theory ◽  
Edge Structure ◽  
X Ray ◽  
First Time ◽  
X Ray Absorption ◽  
Good Agreement

The lattice relaxation around Ga in CdTe is investigated by means of extended X-ray absorption spectroscopy (EXAFS) and density functional theory (DFT) calculations using the linear augmented plane waves plus local orbitals (LAPW+lo) method. In addition to the substitutional position, the calculations are performed for DX- and A-centers of Ga in CdTe. The results of the calculations are in good agreement with the experimental data, as obtained from EXAFS and X-ray absorption near-edge structure (XANES). They allow the experimental identification of several defect structures in CdTe. In particular, direct experimental evidence for the existence of DX-centers in CdTe is provided, and for the first time the local bond lengths of this defect are measured directly.

scholarly journals Recently synthesized (Ti1−xMox)2AlC (0 ≤ x ≤ 0.20) solid solutions: deciphering the structural, electronic, mechanical and thermodynamic properties via ab initio simulations

RSC Advances ◽  
2020 ◽  
Vol 10 (52) ◽  
pp. 31535-31546 ◽  
Author(s):  
M. A. Ali ◽  
S. H. Naqib
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Solid Solutions ◽  
Density Functional ◽  
Functional Theory ◽  
Ab Initio Simulations

The structural, electronic, mechanical and thermodynamic properties of (Ti1−xMox)2AlC (0 ≤ x ≤ 0.20) were explored using density functional theory.

scholarly journals Exploiting superspace to clarify vacancy and Al/Si ordering in mullite

IUCrJ ◽  
2018 ◽  
Vol 5 (4) ◽  
pp. 497-509 ◽  
Author(s):  
Paul Benjamin Klar ◽  
Iñigo Etxebarria ◽  
Gotzon Madariaga
Keyword(s):  
Density Functional ◽  
X Ray Diffraction ◽  
Intrinsic Structure ◽  
Functional Theory ◽  
New Approach ◽  
X Ray ◽  
Vacancy Ordering ◽  
Harmonic Modulation ◽  
First Time

Synchrotron single-crystal X-ray diffraction has revealed diffuse scattering alongside sharp satellite reflections for different samples of mullite (Al4+2xSi2−2xO10−x). Structural models have been developed in (3+1)-dimensional superspace that account for vacancy ordering and Al/Si ordering based on harmonic modulation functions. A constraint scheme is presented which explains the crystal-chemical relationships between the split sites of the average structure. The modulation amplitudes of the refinements differ significantly by a factor of ∼3, which is explained in terms of different degrees of ordering,i.e.vacancies follow the same ordering principle in all samples but to different extents. A new approach is applied for the first time to determine Al/Si ordering by combining density functional theory with the modulated volumes of the tetrahedra. The presence of Si–Si diclusters indicates that the mineral classification of mullite needs to be reviewed. A description of the crystal structure of mullite must consider both the chemical composition and the degree of ordering. This is of particular importance for applications such as advanced ceramics, because the physical properties depend on the intrinsic structure of mullite.

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