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first-principles computation of magnesium doped CaZrO3 perovskite: A study of phase transformation, bandgap engineering and optical response for optoelectronic applications

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SOLID STATE COMMUNICATIONS 2020年 313卷 113907-113907页

作者： Zeba, I. Ramzan, M. Ahmad, Riaz Shakil, M. Rizwan, M. Rafique, M. Sarfraz, M. Ajmal, M. Gillani, S. S. A. Woman Univ Lahore Lahore Coll Dept Phys Lahore 54000 Pakistan Univ Lahore Govt Coll Dept Phys Lahore 54000 Pakistan Univ Gujrat Dept Phys Gujrat 50700 Pakistan Univ Sahiwal Dept Phys Sahiwal 57000 Pakistan

In the present work the structural, electronic and optical properties of pure CaZrO3 have been tuned by the magnesium (Mg) doping concentrations (1.41%, 2.82% and 4.23%) by first-principles computation, based on the density functional theory (DFT), implemented within the CASTEP code with Perdew-Burke-Ernzerhof-Generalized-Gradient-Approximations (PBE-GGA) exchange correlation functional and USP (ultra-soft pseudo potential). From structural results optimized lattice parameters and unit cell volume are obtained, well in match with literature, and with 4.23% doping concentration of Mg structural phase transformation, cubic to pseudo-cubic tetragonal, along with a noticeable influence on electronic band gap squeezing, with the appear-ance of new k-symmetry points at Brillouin zone, is observed. Electronic band structure shows that with, 1.41% and 2.82% doping concentration of Mg, the indirect band gap of host changes to direct one while with 4.23% doping concentration it remains same and value of host band gap is reduced from 3.279eV to 2.189eV. The phase transformation and reduction of band gap is explained with partial and total density of sates and have great influence on the optical properties. Analysis of optical properties with Mg doping reveals that the absorption edges of the doped CaZrO3 show the red shift (1.9eV-0.65eV) whereas the static refractive index almost remain same. Electron energy loss spectra is observed to be consistent with absorption spectra. The doping of Mg concentration changes positively in electronic and optical properties and it would be very potential candidate for optoelectronic applications.

关键词： first-principles computation Phase transformation Band gap engineering Red shift in absorption edge

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first-principles computation of diffusional Mg isotope fractionation in silicate melts

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GEOCHIMICA ET COSMOCHIMICA ACTA 2020年 290卷 27-40页

作者： Luo, Haiyang Karki, Bijaya B. Ghosh, Dipta B. Bao, Huiming Louisiana State Univ Dept Geol & Geophys Baton Rouge LA 70803 USA Louisiana State Univ Sch Elect Engn & Comp Sci Baton Rouge LA 70803 USA Louisiana State Univ Ctr Computat & Technol Baton Rouge LA 70803 USA

Diffusional isotope fractionation occurs in geochemical processes (such as magma mixing, bubble growth, and crystal growth), even at magmatic temperatures. Isotopic mass dependence of diffusion is commonly expressed as Di/Dj = (m(j)/m(i))(beta), where D-i and D-j are diffusion coefficients of two isotopes whose masses are m(i) and m(j). How the dimensionless empirical parameter beta depends on temperature, pressure, and composition remains poorly constrained. Here, we conducted a series of first-principles molecular dynamics simulations to evaluate the beta factor of Mg isotopes in MgSiO3 and Mg2SiO4 melts using pseudo-isotope method. In particular, we considered interactions between Mg isotopes by simultaneously putting pseudo-mass and normalmass Mg atoms in a simulation supercell. The calculated beta for Mg isotopes decreases linearly with decreasing temperature at zero pressure, from 0.158 +/- 0.004 at 4000 K to 0.121 +/- 0.017 at 2200 K for MgSiO3 melt and from 0.150 +/- 0.004 at 4000 K to 0.101 +/- 0.012 at 2200 K for Mg2SiO4 melt. Moreover, our simulations of compressed Mg2SiO4 melt along the 3000 K isotherm show that the beta value decreases linearly from 0.130 +/- 0.006 at 0 GPa to 0.060 +/- 0.011 at 17 GPa. Based on our diffusivity results, the empirically established positive correlation between beta and solvent-normalized diffusivity (D-i/D-Si) seems to be applicable only at constant temperatures or in narrow temperature ranges. Analysis of atomistic mechanisms suggests that the calculated beta values are inversely correlated with force constants of Mg at a given temperature or pressure. Good agreement between our first principles results with available experimental data suggests that interactions between isotopes of major elements must be considered in calculating beta for major elements in silicate melts. Also, we discuss diffusion-controlled crystal growth by considering our calculated beta values. (C) 2020 Elsevier Ltd. All rights reserved.

关键词： Isotope fractionation Diffusivity first-principles computation Silicate melts

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Effect of potassium on the structural, electronic, and optical properties of CsSrF3 fluro perovskite: first-principles computation with GGA-PBE

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OPTIK 2022年 259卷 168741-168741页

作者： Arif, Hina Tahir, M. B. Sagir, M. Alrobei, Hussein Alzaid, Meshal Ullah, Sami Hussien, Mohamed Khwaja Fareed Univ Engn & Informat Technol Dept Phys Rahim Yar Khan Pakistan Khwaja Fareed Univ Engn & Informat Technol Dept Chem Engn Rahim Yar Khan Pakistan Prince Sattam Bin Abdul Aziz Univ Coll Engn Dept Mech Engn Al Kharj Saudi Arabia Jouf Univ Coll Sci Phys Dept POB 2014 Sakaka Saudi Arabia King Khalid Univ Coll Sci Dept Chem POB 9004 Abha 61413 Saudi Arabia

Here, we computed ground state structural, electronic, and optical properties for ABX3 type Fluro perovskite structure due to enhancing photovoltaic, and owing to solar cell applications. Exploring the effect of K doping on CsSrF3 Perovskite, implemented CASTEP code for first principles calculations based on DFT along with generalized gradient approximation (GGA) with Perdew Burke Ehrenzorf (GGA-PBE) exchange-correlation potential and ultra-soft pseudo plane wave. Effect of doping at "Cs " sites on electronic structure have been studied here. The compound has a stable cubic pm3m structure with a supercell of 2 x 2 x 1. Doping of "K " at "Cs " site influenced the electronic band structure of CsSrF3 notably by decreasing bandgap and transforming it from indirect bandgap to direct, partial density of state also changes with doping concentration and move towards conduction band. CsSrF3 gives enhanced optical properties and the reduction of bandgap makes it a favorable candidate for optoelectronic and photovoltaic devices.

关键词： first-principles computation Fluorine Perovskite Optical properties

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Study the effect of magnesium doping concentration on structural and optoelectronic response of NaCa1-xMgxF3 fluoro-perovskite: first-principles computation

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OPTIK 2020年 218卷 164990-164990页

作者： Zeba, I. Kiran, R. Shakil, M. Rafique, M. Ahmad, Riaz Gillani, S. S. A. Lahore Coll Woman Univ Lahore Dept Phys Lahore 54000 Pakistan Govt Coll Univ Lahore Dept Phys Lahore 54000 Pakistan Univ Gujrat Dept Phys Gujrat 50700 Pakistan Univ Sahiwal Dept Phys Sahiwal 57000 Pakistan

Methodology of all-electron self-consistent ultra-soft pseudopotential plane wave in PBE Generalized Gradient density approximations have been applied to investigate structural, electronic and optical properties of cubic pure and magnesium doped NaCaF3 fluoro-perovskite. Our evaluated optimized structural parameters for pure NaCaF3 are well in agreement with the already reported results and optimized structural parameters for magnesium doped (1.41 %, 2.82 % and 4.23 %) NaCaF3 are reported first time. The electronic band structure calculation for pure and magnesium doped NaCaF3 has revealed a direct band transition with the bandgap values of 4.773 eV-3.325 eV, respectively. The degree of localized electrons in different bands is confirmed by total and partial densities of states. The transitions in optical properties of pure and magnesium doped NaCaF3 material were recognized by assigning corresponding peaks obtained and are discussed in line of structural-electronic determinations. This is the first theoretical study of cubic crystal structure of magnesium doped NaCaF3 as far as we know.

关键词： first-principles computation Structural optimization Band gap tuning Direct Band transition Red shift in absorption edge

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first-principles computation of mantle materials in crystalline and amorphous phases

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PHYSICS OF THE EARTH AND PLANETARY INTERIORS 2015年 240卷 43-69页

作者： Karki, Bijaya B. Louisiana State Univ Ctr Computat & Technol Dept Geol & Geophys Sch Elect Engn & Comp Sci Baton Rouge LA 70803 USA

first-principles methods based on density functional theory are used extensively in the investigation of the behavior and properties of mantle materials over broad ranges of pressure, temperature, and composition that are relevant. A review of computational results reported during the last couple of decades shows that essentially all properties including structure, phase transition, equation of state, thermodynamics, elasticity, alloying, conductivity, defects, interfaces, diffusivity, viscosity, and melting have been calculated from first principles. Using MgO, the second most abundant oxide of Earth's mantle, as a primary example and considering many other mantle materials in their crystalline and amorphous phases, we have found that most properties are strongly pressure dependent, sometimes varying non-monotonically and anomalously, with the effects of temperature being systematically suppressed with compression. The overall agreement with the available experimental data is excellent;it is remarkable that the early-calculated results such as shear wave velocities of two key phases, MgO and MgSiO3 perovskite, were subsequently reproduced by experimentation covering almost the entire mantle pressure regime. As covered in some detail, the defect formation and migration enthalpies of key mantle materials increase with pressure. The predicted trend is that partial MgO Schottky defects are energetically most favorable in Mg-silicates but their formation enthalpies are high. So, the diffusion in the mantle is likely to be in the extrinsic regime. Preliminary results on MgO and forsterite hint that the grain boundaries can accommodate point defects (including impurities) and enhance diffusion rates at all pressures. The structures are highly distorted in the close vicinity of the defects and at the interface with excess space. Recent simulations of MgO-SiO2 binary and other silicate melts have found that the melt self-diffusion and viscosity vary by several orders of mag

关键词： first-principles computation Mantle materials High pressure Defects Silicate liquids

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Modulation of titanium dioxide/graphene interface by Mg2+doping: Titanium dioxide coatings with conductive, corrosion-resistant and superhydrophobic features

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ENERGY 2025年 317卷

作者： Liu, Ze Zhou, Kexin Wang, Junbo Peng, Chong Li, Yun Yang, Shuyi Tao, E. Bohai Univ Inst Ocean Res Inst Environm Res Coll Chem & Mat EngnLiaoning Key Lab Chem Clean P Jinzhou 121013 Liaoning Peoples R China Baoti Huashen Titanium Ind Co Ltd Jinzhou 121000 Liaoning Peoples R China Yantai Univ Chem & Chem Engn Coll Yantai 264005 Shandong Peoples R China Dalian Univ Technol Sch Chem Engn State Key Lab Fine Chem Dalian 116024 Liaoning Peoples R China

Conductive coatings show great application potential in the fields of electronic devices, energy storage and conversion, and primers for new energy vehicles, but their performance bottlenecks such as corrosion resistance, hydrophobicity, and dispersibility limit their wide applications. In order to solve these problems, this paper innovatively proposes a conductive coating (Mg-TG) composite of titanium dioxide and graphene via Mg2+ modification in the acetic acid system. By precisely modulating the doping amount of Mg2+, the electronic structure and physical properties of titanium dioxide are significantly optimised, and an efficient conductive network is formed with graphene, successfully constructing a high-performance composite powder with a low resistivity as low as 0.083 Omega cm. Advanced characterisation techniques (XPS) and density-functional-theoretic calculations (DFT) indicate that the formation of defective engineering activates lattice oxygens, leading to electronic structure modulation and material valence bonding changes, thus constructing efficient electron transport channels (Ti-O-C, Mg-O-C) and ensuring uniform distribution and fast electron circulation in the coating. In addition, through the Tafel curve test, water contact angle test (WCA) and coating experiments, it was demonstrated that the Mg2+ modification effectively improved the corrosion resistance, hydrophobicity and dispersibility of the material. In this way, the coating not only effectively resists the ability of corrosive media and extends its service life, but also maintains stable electrical properties in humid environments and avoids performance degradation due to moisture penetration. At the same time, the modification of Mg2+ also promotes the uniform dispersion of the material and improves the activity and stability of the coating, laying a solid foundation for efficient performance in a variety of application scenarios.

关键词： Mg 2+doping Graphene Coating Electrical conductivity first-principles computation

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first-principles calculations on structural stability and electronic properties of the Strontium-Argon System at High Pressure

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computationAL MATERIALS SCIENCE 2025年 248卷

作者： Liu, Xu Wei, Shuli Gao, Xinlei Guo, Yanhui Liu, Siyu Ju, Xiaoshi Chang, Qiang Sun, Yuping Shandong Univ Technol Sch Phys & Optoelect Engn Zibo 250049 Peoples R China

In order to explore the mechanism behind the stability of noble gas (NG) element compounds and make a systematic theoretical predictions for alkaline earth metal NG elements compounds, this paper focuses on the reaction of NG elements with alkaline earth metals. An in-depth theoretical predictions of the Sr-Ar system has been carried out by using the structure prediction method CALYPSO, to search for possible stable structures at different pressures. The structure optimizations and property analyses have been performed by first-principles calculation VASP code. We have discovered two hitherto unknown structures: the structure of Cmcm-SrAr and I 4/ mmm-SrAr 3 . The Cmcm-SrAr is stable in the pressure range of 150-210 GPa, while the I 4/ mmm-SrAr 3 is stable in the pressure range of 190-300 GPa. Additionally, two metastable structures have been discovered under ultrahigh pressure (UHP) conditions: P 6 3 / mmc-SrAr and P 2 1 / m-SrAr 4 . The analysis of the electronic band structure and density of states (DOS) of the four Sr-Ar compounds reveals that they all exhibit metallicity and are mainly contributed by the Sr-d orbitals near the Fermi level, which plays a crucial role in maintaining the stability of the crystals. In this paper, the superconducting properties of Sr-Ar structures are investigated for the first time, and it is found that these compounds are superconducting. The research findings will substantially enhance our understanding of the structural evolution in NG element compounds under high pressure.

关键词： first-principles computation High pressure NG element compound

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first-principles investigation on solute co-segregations and their strengthening grain boundary roles in stable nanocrystalline copper

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ADVANCED COMPOSITES AND HYBRID MATERIALS 2024年第5期7卷 1-12页

作者： Shi, Yanyan Alshammari, Dalal A. Lei, Chao Thabet, Hamdy Khamees Xue, Hongtao Tang, Fuling Lanzhou Univ Technol Sch Mat Sci & Engn State Key Lab Adv Proc & Recycling Nonferrous Met Lanzhou 730050 Peoples R China Lanzhou City Univ Sch Bailie Mech Engn Lanzhou 730050 Peoples R China Univ Hafr Al Batin Coll Sci Dept Chem POB 39524 Hafar al Batin Saudi Arabia Northern Border Univ Coll Sci & Arts Dept Chem Rafha 91911 Saudi Arabia

Regulating the grain boundaries (GBs) via solute segregation provides a viable pathway to design stable nanocrystalline metals. This study investigates the segregation tendencies of X (X = In, Cr, Ca, Co, Zn, Ag, Zr, and Sn) at the potential sites of Cu Sigma 11 [110](11\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\overline{1}$$\end{document}3) GB, as well as the co-segregation behavior of Y (Y = Cr and Co) at the Zr- and Ca-segregated Cu GBs, using first-principles calculations. Our results indicate that Cr and Co lack a thermodynamic driving force for segregating to Cu GBs, unlike other elements possessing GB segregation tendencies. The co-segregation calculations show that the presence of Zr at Cu GB can induce the segregation of Cr and Co. In comparison to the single-solute segregation of Zr, Cr, and Co, Zr-Co and Zr-Cr co-segregations exhibit synergistic enhancing effect on the GB thermodynamic stability. Regarding to the enhancement of GB fracture strength, Zr-Co co-segregation shows antagonistic effect, whereas Zr-Cr co-segregation demonstrates synergistic action. This work sheds light on accurately regulating the GB stability and strength of nanograined Cu alloys based on GB segregation.

关键词： Nanograined Cu alloys Single-solute segregation Co-segregation first-principles computation Tensile test, Grain boundary strength and stability

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Characterization and modeling studies towards Al_(3)Ti/Mg interfaces in Ti reinforced AZ31 alloys

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Journal of Materials Science & Technology 2023年第16期147卷 197-206页

作者： Longke Bao Shengli Han Shengkun Xi Yuhui Zhang Cuiping Wang Kaihong Zheng Rongpei Shi Xingjun Liu Fusheng Pan State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyShenzhen 518055China College of Materials Science and Engineering and Institute of Materials Genome and Big DataHarbin Institute of TechnologyShenzhen 518055China Institute of New Materials Guangdong Academy of SciencesGuangzhou 510650China College of Materials Science and Engineering Xiamen UniversityXiamen 361005China College of Materials Science and Engineering Chongqing UniversityChongqing 400045China

The interfaces between in-situ Al3Ti particles and magnesium(Mg)matrix are crucial role in highperformance titanium(Ti)reinforced AZ31 ***,the interfaces between Al3Ti particles and the Mg matrix are fabricated and investigated using advanced characterization tools and first-principles *** orientation relationship(OR)and atomic interface structure between the Al_(3)Ti particles and matrix are characterized using a high-resolution transmission electron *** OR is determined to be(1010)Mg//(001)Al3Ti;[1213]Mg//[100]*** on the characterized OR,the interface properties(including atomic structure,work of adhesion,interface energy,and fracture mechanism)are investigated using first-principles *** relaxed interface structure indicates that the TiAl-terminated bridge site configurations(MT1)and hollow site configurations(HCP1)are unstable and would convert into other bridge site configurations(MT).Furthermore,the work of adhesion and interface energy suggests that Al-terminated hollow site configurations(HCP)and bridge site configurations(MT)are more stable than other *** addition,the calculations of work of fracture show that fracture of the interfaces with Al-MT1,Al-HCP,and TiAl-MT configurations may initiate from bulk Mg *** findings may help to understand and tailor the deformation mechanisms and mechanical properties of Ti-reinforced Mg alloys.

关键词： Ti/AZ31 alloy Mg/Al_(3)Ti interface HAADF-STEM first-principles computation

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How High Does the Pressure Need to Be to Produce Internoble-Gas Ionic Compounds?

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CCS Chemistry 2025年第5期7卷 1359-1368页

作者： Zhongyu Wan Cheng-wei Ju Tianyi Yang Wenjun Xu Bo Li Ruiqin Zhang Xiao Cheng Zeng Department of Physics City University of Hong KongHong Kong SAR 999077 Pritzker School of Molecular Engineering The University of ChicagoChicagoIllinois 60637 Division of Chemistry and Chemical Engineering California Institute of TechnologyPasadenaCalifornia 91125 Department of Materials Science and Engineering City University of Hong KongHong Kong SAR 999077

Noble gases(NGs)are widely distributed in the universe with billions-year long lifetimes due to their closed-shell electronic structures with little chemical *** studies have found that most NGs can form covalent or ionic compounds with openshell neutral atoms(e.g.,O,Fe,and Ni)in conditions similar to planetary ***,there are still rare reports of chemical bonding among NG elements *** date,NG solids with only weak intermolecular interactions have been ***,we present the first theoretical evidence of the formation of inter-NG ionic compounds beyond terapascal(TPa)*** performed ab-initio computations combined with crystal-structure predictions and showed that Kr and Xe can act as oxidant and reductant,respectively,above 1.5 ***,the conventional octet rule for chemical compounds is inapplicable here due to the abnormal charge transfer upon ionic bond *** work not only addresses a fundamental chemistry question about how high the pressure needs to be for NG elements to form chemical compounds,but it also predicts the intriguing superconductivity of the inter-NG *** required extreme environment for the formation of inter-NG ionic compounds can be found in gas giants,like the planets Jupiter and Saturn,if ultrahigh pressure(>1.5 TPa)is available near the core region.

关键词： high pressure physics and chemistry chemical reactivity noble gases ionic bond gas giant superconductivity first-principles computation

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