We investigate the phase diagram of the heterostructural solid solution (InxGa1-x)2O3 both computationally, by combining cluster expansion and density functional theory, and experimentally, by means of TEM measurements of pulsed laser deposited (PLD) heteroepitaxial thin films. The shapes of the Gibbs free energy curves for the monoclinic, hexagonal and cubic bixbyite alloy as a function of composition can be explained in terms of the preferred cation coordination environments of indium and gallium. We show by atomically resolved STEM that the strong preference of indium for six-fold coordination results in ordered monoclinic and hexagonal lattices. This ordering impacts the configurational entropy in the solid solution and thereby the (InxGa1-x)2O3 phase diagram. The resulting phase diagram is characterized by very limited solubilities of gallium and indium in the monoclinic, hexagonal and cubic ground state phases respectively but exhibits wide metastable ranges at realistic growth temperatures. On the indium rich side of the phase diagram a wide miscibility gap is found, which results in phase separated layers. The experimentally observed indium solubilities in the PLD samples are in the range of x=0.45 and x=0.55 for monoclinic and hexagonal single-phase films, while for phase separated films we find x=0.5 for the monoclinic phase, x=0.65-0.7 for the hexagonal phase and x>0.9 for the cubic phase. These values are consistent with the computed metastable ranges for each phase.
The presence of lone pair (LP) electrons is strongly associated with the disruption of lattice heat transport, which is a critical component of strategies to achieve efficient thermoelectric energy conversion. By exploiting an empirical relationship between lattice thermal conductivity $κ_L$ and the bond angles of pnictogen group LP cation coordination environments, we develop an inverse design strategy based on a materials database screening to identify chalcogenide materials with ultralow $κ_L$ for thermoelectrics. Screening the $\sim$ 635,000 real and hypothetical inorganic crystals of the …
Antiferromagnetic PbMnTeO6, also known as mineral kuranakhite, has been reported recently to have all three cations in trigonal prismatic coordination, which is extremely unusual for both Mn(4+) and Te(6+). In this work, the phase was reproduced with the same lattice parameters and Néel temperature TN = 20 K. However, powder neutron diffraction unambiguously determined octahedral (trigonal antiprismatic) coordination for all cations within the chiral space group P312. The same symmetry was proposed for SrMnTeO6 and PbGeTeO6, instead of the reported space groups P-62m and P31m, respectively. Pb…
We have analyzed bond-length distributions between cations and anions for crystal structures in the crystallographic open database (www.crystallography.net/cod/). The distributions are classified by the coordination environments of cations, which are determined by a tool named as Chemenv (Acta Cryst. (2020). B76, 683-695).
The computational design of materials with ionic bonds poses a critical challenge to thermodynamic modeling since density functional theory yields inaccurate predictions of their formation enthalpies. Progress requires leveraging physically insightful correction methods. The recently introduced coordination corrected enthalpies (CCE) method delivers accurate formation enthalpies with mean absolute errors close to room temperature thermal energy, i.e., 25meV/atom. The CCE scheme, depending on the number of cation-anion bonds and oxidation state of the cation, requires an automated analysis of t…
A quantitative geometric predictor for the dimensionality of magnetic interactions is presented. This predictor is based on networks of superexchange interactions and can be quickly calculated for crystalline compounds of arbitrary chemistry, occupancy, or symmetry. The resulting data is useful for classifying structural families of magnetic compounds. Starting with 42,520 compounds, we have classified and quantified compounds with $3d$ transition metal cations. The predictor reveals trends in magnetic interactions that are often not apparent from the space group of the compounds, such as tric…
The correct calculation of formation enthalpy is one of the enablers of ab-initio computational materials design. For several classes of systems (e.g. oxides) standard density functional theory produces incorrect values. Here we propose the "Coordination Corrected Enthalpies" method (CCE), based on the number of nearest neighbor cation-anion bonds, and also capable of correcting relative stability of polymorphs. CCE uses calculations employing the Perdew, Burke and Ernzerhof (PBE), Local Density Approximation (LDA) and Strongly Constrained and Appropriately Normed (SCAN) exchange correlation f…
Bi-S network origin of cation-disorder stability and dispersive band edges in AgBiS2
Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences（中国科学院宁波材料技术与工程研究所）；The Hong Kong University of Science and Technology (Guangzhou)（香港科技大学（广州））；Eastern Institute of Technology（东方理工大学）；Beijing Computational Science Research Center（北京计算科学研究中心）
Pressure induced structural transitions, coordination crossover, and optoelectronic response in divalent metavanadate CaV$_2$O$_6$
Indian Institute of Science Education and Research Kolkata（印度科学教育研究学院加尔各答分校）；National Centre for High-Pressure Studies（高压研究中心）；IMPMC, Sorbonne Université（巴黎第六大学地球物理学研究所）；Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Deutsches Elektronen Synchrotron（德国电子同步辐射中心）
Strain engineering with different substrate facets is promising for tuning functional properties of thin film perovskite oxides. By choice of facet, different surface symmetries and chemical bond directions for epitaxial interfaces can be tailored. Here, preparation of well-defined pseudo-cubic (111)-oriented orthorhombic substrates of DyScO3 , GdScO3 , and NdGaO3 is reported. The choice of orthorhombic facet, (011)o or (101)o , both corresponding to pseudo-cubic (111)pc , gives vicinal surfaces with single or double (111pc layer terrace step heights, respectively, impacting subsequent thin fi…
Investigating the impact of copper-PEDOT:PSS matrix towards non-enzymatic electrochemical creatinine detection
Institute of Physical Chemistry, Polish Academy of Sciences（波兰科学院物理化学研究所）；Department of Electronic and Electrical Engineering, University of Sheffield（谢菲尔德大学电子与电气工程系）；University of Warsaw, Faculty of Chemistry（华沙大学化学系）；Centre for Advanced Materials and Technologies CEZAMAT, Warsaw University of Technology（华沙理工大学先进材料与技术中心CEZAMAT）
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 p…
Amorphous calcium carbonate (ACC) has been widely found in biomineralization, both as a transient precursor and a stable phase, but how organisms accurately control its formation and crystallization pathway remains unclear. Here, we aim to illu-minate the role of biologically relevant additives on the phase behaviour of calcium carbonate solution by investigating their effects on the formation of ACC. Results show that divalent cations like magnesium (Mg2+) ions and negatively charged small organic molecules like aspartic acid (Asp) have little/no effect on ACC formation. However, the particle…
