We present the structural, electronic, vibrational, and photoluminescence properties of polycrystalline LaV$_{1-x}$Nb$_x$O$_4$ ($x =$ 0--0.2) samples at room temperature. The substitution of Nb at the V site shows the fascinating structural and optical behavior due to their isoelectronic character and larger ionic radii of Nb$^{5+}$ as compared to the V$^{5+}$. The Rietveld refinement of x-ray diffraction patterns demonstrate that the $x=$ 0 sample exist in a monoclinic (P2$_1$/n) phase, whereas for the $x >$ 0, both monoclinic and scheelite-tetragonal (I4$_1$/a) phases co-exist in a certain proportion. Interestingly, a monotonous enhancement in the Raman spectral intensity with Nb substitution is correlated with the substitution induced increase in the scheelite-tetragonal phase. The x-ray absorption measurements reveal that the La ions exist in a trivalent oxidation state, while V and Nb cations possess 5+ oxidation state in tetrahedral coordination. Moreover, the Fourier-transform infrared (FTIR) spectra indicate that the Nb substitution give origin to some additional IR modes owing to the deformation of the VO$_4$$^{3-}$ tetrahedra and mixing of monoclinic and tetragonal phases. The photoluminescence measurements on these samples exhibit broadband spectra and their deconvolution designate the availability of more than one electron-hole pairs recombination center.
We show that the $t_{2g}^2$ perovskite LaVO$_3$, in its orthorhombic phase, is a rare case of a system hosting an orbital-ordering Kugel-Khomskii phase transition, rather than being controlled by the Coulomb-enhanced crystal-field splitting. We find that, as a consequence of this, the magnetic transition is close to (and even above) the super-exchange driven orbital-ordering transition, whereas typically magnetism arises at much lower temperatures than orbital ordering. Our results support the experimental scenario of orbital-ordering and G-type spin correlations just above the monoclinic-to-o…
We present the structural ordering and the associated physical behavior of a Ni-Mn-Si Laves phase, Mn(Ni$_{0.6}$Si$_{0.4})_2$. The high-resolution transmission electron microscopy and electron energy loss spectroscopy analysis were performed to resolve a distinct atomic ordering of the system. The study determined the origin of the short-range ordering to be the unique arrangement between Ni and Si atoms. The study also presents the atomic resolution mapping of the Si atoms which has never been reported by any previous studies. With further electrical conductivity measurement, we find one of t…
Metallic Bonding-Driven Elastic Softness and Optical Response in the Mg-Rich Laves-Phase LaMg2
Pabna Textile Engineering College, Bangladesh University of Textiles（帕尔纳纺织工程学院，孟加拉国纺织大学）；EcoBengal Centre for Materials and Energy Research（生态孟加拉材料与能源研究中心）；Bangladesh Atomic Energy Regulatory Authority (BAERA)（孟加拉国原子能监管局）；Department of Physics, University of Barishal（巴里萨尔大学物理系）；Department of Electrical and Mechanical Engineering, Nagoya Institute of Technology（名古屋工业大学电气与机械工程系）；School of Materials Science and Engineering, Faculty of Science, University of New South Wales（新南威尔士大学理学院材料科学与工程系）
Physical and Dielectric Properties of Polycrystalline LaV$_{0.5}$Nb$_{0.5}$O$_4$
Delhi Technological University（德里理工大学）；Atma Ram Sanatan Dharma College, University of Delhi（德里大学阿特玛·拉姆·萨纳坦·达尔玛学院）；Indian Institute of Technology Delhi（德里印度理工学院）；Inter-University Accelerator Center（校际加速器中心）；Hindu College, University of Delhi（德里大学印度教学院）
Screened hybrid functional applied to 3d^0-->3d^8 transition-metal perovskites LaMO3 (M=Sc-Cu): influence of the exchange mixing parameter on the structural, electronic and magnetic properties
We present a systematic investigation of the role and importance of excitonic effects on the optical properties of transitions metal oxide perovskites. A representative set of fourteen compounds has been selected, including 3$d$ (SrTiO$_3$, LaScO$_3$, LaTiO$_3$, LaVO$_3$, LaCrO$_3$, LaMnO$_3$, LaFeO$_3$ and SrMnO$_3$), 4$d$ (SrZrO$_3$, SrTcO$_3$ and Ca$_2$RuO$_4$) and 5$d$ (SrHfO$_3$, KTaO$_3$ and NaOsO$_3$) perovskites, covering a band gap ranging from 0.1 eV to 6.1 eV and exhibiting different electronic, structural and magnetic properties. Optical conductivities and optical transitions inclu…
Investigation on different physical aspects such as structural, elastic, mechanical, optical properties and Debye temperature of Fe2ScM (M = P and As) semiconductors: a DFT based first principles study
We report on the growth of Y2Ti2O7 single crystals by optical floating zone technique. X-ray diffraction and Raman spectroscopy studies confirm the structural quality of the crystal. The UV-Vis optical studies reveal that the grown crystals have a high optical transparency with an optical band gap of 3.44 eV. The hardness of Y2Ti2O7 single crystal is measured for the first time using nanoindentation. The measured hardness, indentation and bulk modulus are found to be 16.4$\pm$0.4, 321.1$\pm$6.9 and 243.3$\pm$5.2 GPa respectively, which are higher than its polycrystalline counterpart and its co…
In this work, we report the effects of calcination temperature on structural, dielectric, semiconducting and optical properties of YFeO3 nanoparticles prepared by a high energy ball milling process. The structural analysis of the X-ray diffraction data shows that YFeO3 exists in orthorhombic as well as in hexagonal mixed-phase states. The Rietveld analysis confirms that orthorhombic YFeO3 crystallizes into Pnma space group. The optical band gap of YFeO3 reduces from 1.96 eV to 1.68 eV with increasing the calcination temperature of the YFeO3 sample. The bandgap reducing effect might be attribut…
Comments on the paper: Growth structural, spectral, optical and mechanical studies of gamma bis glycinium oxalate (GBGOx) new NLO single crystal by SEST method
Here, we report structural and optical properties of (ALa)(FeMn)O6 (A = Ba and Sr) double perovskite synthesized via auto-combustion followed by a calcination process. Rietveld refinement of the structure using x-ray diffraction data reveals that (BaLa)(FeMn)O6 crystallizes into cubic crystal structure with space group Pm-3m while (SrLa)(FeMn)O6 crystallizes into rhombohedral crystal structure having space group R-3c. The absorption spectrum measurement using UV-Vis spectroscopy reveals that these samples are perfect insulator having an energy band gap between conduction and valence band of th…
Investigation on Vibrational, Optical and Structural Properties of an Amorphous Se$_{0.80}$S$_{0.20}$ Alloy Produced by Mechanical Alloying
用Raman光谱、X射线衍射、扩展X射线吸收精细结构（EXAFS）和光学吸收光谱研究了机械合金化法制备的非晶态Se $_{0.80}$ S $_{0.20}$合金，并对其总结构因子和EXAFS数据进行了反向蒙特卡罗模拟。它的振动模式，光学间隙和平均原子间距离和平均配位数的结构特性进行了测定和比较，发现为非晶硒$_{0.90}$ S $_{0.10}$合金。结果表明，配位数，原子间距离和间隙能量依赖于硫浓度。
Optical reflectivity as a simple diagnostic method for testing structural quality of icosahedral quasicrystals 2 The optical reflectivity of Al-based and Ti-based quasicrystalline and approximant samples were investigated versus the quality of their structural morphology using optical reflectometry, X-ray diffraction and transmission electron microscopy. The different structural morphologies were obtained using three different preparation processes : sintering, pulsed laser deposition and reactive cathodic magnetron sputtering. The work demonstrates that the canonical behaviour of icosahedral …
The structural, electrical, optical, and mechanical characteristics of the lead-free halide double perovskites Cs2NaTlX6 X = F, Cl, Br are calculated by utilizing PBE functional within generalized gradient approximation GGA under the context of density functional theory DFT.The structural properties such as lattice parameter, cell volume, total energy, bulk modulus, pressure derivative, and tolerance factor are computed at equilibrium.The electronic density of states reveals the semiconducting nature of the compound and the band structure exhibits the nature of the band gap to be direct.HSE06 …
Comprehensive investigation on the correlation of growth, structural and optical properties of GaN nanowires grown on Si(111) substrates by plasma assisted molecular beam epitaxy technique
We computed structural, elastic, electronic and optical properties of Be2X(X = C; Si; Ge; Sn) family of antiuorite with ab initio DFT calculations using the generalized gradient approximation (GGA). The different parameters such as geometry optimization, band structure, density of states, elastic constants, dielectric functions have been studied. We also calculated bandgap using PBE0 and HSE hybrid functionals to compare experimental bandgap of Be2C. Although three of the compounds are hypothetical in nature, their formation energy found to be negative. The calculated values of elastic constan…
Ab-initio study of structural, elastic, electronic, optical and thermodynamic properties of MgV2O6
采用基于密度泛函理论（DFT）的平面波紫外赝势方法，对正交MgV 2 O 6的结构、力学、电子、光学和热力学性质进行了从头计算.计算的晶格参数与实验数据符合得很好。计算了二阶弹性常数和其它相关量，如杨氏模量、剪切模量、泊松比、压缩系数、各向异性因子、声速和德拜温度。在分析计算的弹性常数后，表明所研究的化合物是机械稳定的。电子能带结构分析表明，该化合物具有半导体性质，带隙为2.195 eV，主要来自O-2s态。
We report on structural and optical properties of InGaN/GaN thin films, with a 0.46o misalignment between the surface and the (0001) plane, which were grown by metal-organic chemical vapor deposition (MOCVD) on 0.34o miscut sapphire substrates. X-ray diffraction and X-ray reflectivity were used to precisely measure the degree of miscut. Reciprocal space mapping was employed to determine the lattice parameters and strain state of the InGaN layers. Rutherford backscattering spectrometry with channeling was employed to measure their composition and crystalline quality with depth resolution. No st…
We report emergence of photoluminescence at room temperature in trigonal $Cs_3Bi_2Br_9$ at high pressures. Enhancement in intensity with pressure is found to be driven by increase in distortion of $BiBr_6$ octahedra and iso-structural transitions. Electronic band structure calculations show the sample in the high pressure phase to be an indirect band gap semiconductor. The luminescence peak profile show signatures related to the recombination of free and self trapped excitons, respectively. Blue shift of the both peaks till about 4.4 GPa are due to the exciton recombination before relaxation d…
