Ab Initio Determination Research Articles

Atomic-resolution structures from polycrystalline covalent organic frameworks with enhanced cryo-cRED

The pursuit of atomic precision structure of porous covalent organic frameworks (COFs) is the key to understanding the relationship between structures and properties, and further developing new materials with superior performance. Yet, a challenge of how to determine their atomic structures has always existed since the first COFs reported seventeen years ago. Here, we present a universal method for ab initio structure determination of polycrystalline three-dimensional (3D) COFs at atomic level using enhanced cryo-continuous rotation electron diffraction (cryo-cRED), which combines hierarchical cluster analysis with cryo-EM technique. The high-quality datasets possess not only up to 0.79-angstrom resolution but more than 90% completeness, leading to unambiguous solution and precise refinement with anisotropic temperature factors. With such a powerful method, the dynamic structures with flexible linkers, degree of interpenetration, position of functional groups, and arrangement of ordered guest molecules are successfully revealed with atomic precision in five 3D COFs, which are almost impossible to be obtained without atomic resolution structure solution. This study demonstrates a practicable strategy for determining the structures of polycrystalline COFs and other beam-sensitive materials and to help in the future discovery of novel materials on the other.

How to get maximum structure information from anisotropic displacement parameters obtained by three-dimensional electron diffraction: an experimental study on metal-organic frameworks.

Three-dimensional electron diffraction (3D ED) has been used for ab initio structure determination of various types of nanocrystals, such as metal-organic frameworks (MOFs), zeolites, metal oxides and organic crystals. These crystals are often obtained as polycrystalline powders, which are too small for single-crystal X-ray diffraction (SCXRD). While it is now possible to obtain accurate atomic positions of nanocrystals by adopting kinematical refinement against 3D ED data, most new structures are refined with isotropic displacement parameters (U eq), which limits the detection of possible structure disorders and atomic motions. Anisotropic displacement parameters (ADPs, Uij ) obtained by anisotropic structure refinement, on the other hand, provide information about the average displacements of atoms from their mean positions in a crystal, which can provide insights with respect to displacive disorder and flexibility. Although ADPs have been obtained from some 3D ED studies of MOFs, they are seldom mentioned or discussed in detail. We report here a detailed study and interpretation of structure models refined anisotropically against 3D ED data. Three MOF samples with different structural complexity and symmetry, namely ZIF-EC1, MIL-140C and Ga(OH)(1,4-ndc) (1,4-ndcH2 is naphthalene-1,4-dicarboxylic acid), were chosen for the studies. We compare the ADPs refined against individual data sets and how they are affected by different data-merging strategies. Based on our results and analysis, we propose strategies for obtaining accurate structure models with interpretable ADPs based on kinematical refinement against 3D ED data. The ADPs of the obtained structure models provide clear and unambiguous information about linker motions in the MOFs.

Ab initio phasing macromolecular structures using electron-counted MicroED data

Structures of two globular proteins were determined ab initio using microcrystal electron diffraction (MicroED) data that were collected on a direct electron detector in counting mode. Microcrystals were identified using a scanning electron microscope (SEM) and thinned with a focused ion beam (FIB) to produce crystalline lamellae of ideal thickness. Continuous-rotation data were collected using an ultra-low exposure rate to enable electron counting in diffraction. For the first sample, triclinic lysozyme extending to a resolution of 0.87 Å, an ideal helical fragment of only three alanine residues provided initial phases. These phases were improved using density modification, allowing the entire atomic structure to be built automatically. A similar approach was successful on a second macromolecular sample, proteinase K, which is much larger and diffracted to a resolution of 1.5 Å. These results demonstrate that macromolecules can be determined to sub-ångström resolution by MicroED and that ab initio phasing can be successfully applied to counting data.

Differential Cross Sections for Cold, State-to-State Spin-Orbit Changing Collisions of NO(v = 10) with Neon.

Inelastic scattering processes have proven a powerful means of investigating molecular interactions, and much current effort is focused on the cold and ultracold regime where quantum phenomena are clearly manifested. Studies of collisions of the open shell nitric oxide (NO) molecule have been central in this effort since the pioneering work of Houston and co-workers in the early 1990s. State-to-state scattering of vibrationally excited molecules in the cold regime introduces challenges that test the suitability of current theoretical methods for ab initio determination of intermolecular potentials, and concomitant electronically nonadiabatic processes raise the bar further. Here we report measurements of differential cross sections for state-to-state spin-orbit changing collisions of NO (v = 10, Ω″ = 1.5, and j″ = 1.5) with neon from 2.3 to 3.5 cm-1 collision energy using our recently developed near-copropagating beam technique. The experimental results are compared with those obtained from quantum scattering calculations on a high-level set of coupled cluster potential energy surfaces and are shown to be in good agreement. The theoretical results suggest that distinct backscattering in the 2.3 cm-1 case arises from overlapping resonances.

Polymorphism and sodium-ion conductivity of NaTa2PO8 synthesized via the Li+/Na+ ion-exchange reaction of LiTa2PO8

Ion exchange reaction is a promising method to explore metastable compounds that could not be synthesized by conventional high-temperature solid-phase reactions. Herein, a new sodium tantalum phosphate, NaTa2PO8 was synthesized via the Li+/Na+ ion-exchange reaction of the parent compound, LiTa2PO8 in molten NaNO3 medium. NaTa2PO8 underwent an irreversible phase transition from the low- (LT-NaTa2PO8) to the high-temperature polymorph (HT-NaTa2PO8) at approximately 1000 °C. The crystal structures were solved using an ab initio structural determination method based on synchrotron X-ray powder diffraction data. The LT-NaTa2PO8 presented an orthorhombic structure, closely related to that of the parent LiTa2PO8 structure. In contrast, the HT-NaTa2PO8 was found to adopt a monoclinic structure, belonging to a family of monophosphate tungsten bronzes with pentagonal tunnels. The ionic conductivities of LT-NaTa2PO8 (σ = 5 × 10−5 S/cm at 309 °C) and HT-NaTa2PO8 (σ = 2 × 10−7 S/cm at 300 °C) exhibited Arrhenius behavior with activation energies of 0.49 and 0.79 eV, respectively. Bond valence energy landscape (BVEL) calculations indicated that a three-dimensional (3D) conduction pathway is formed in LT-NaTa2PO8 structure, while the conduction pathway in HT-NaTa2PO8 shows a two-dimensional (2D) character.

Dimerization-dependent membrane tethering by Atg23 is essential for yeast autophagy.

SUMMARYEukaryotes maintain cellular health through the engulfment and subsequent degradation of intracellular cargo using macroautophagy. The function of Atg23, despite being critical to the efficiency of this process, is unclear due to a lack of biochemical investigations and an absence of any structural information. In this study, we use a combination of in vitro and in vivo methods to show that Atg23 exists primarily as a homodimer, a conformation facilitated by a putative amphipathic helix. We utilize small-angle X-ray scattering to monitor the overall shape of Atg23, revealing that it contains an extended rod-like structure spanning approximately 320 Å. We also demonstrate that Atg23 interacts with membranes directly, primarily through electrostatic interactions, and that these interactions lead to vesicle tethering. Finally, mutation of the hydrophobic face of the putative amphipathic helix completely precludes dimer formation, leading to severely impaired subcellular localization, vesicle tethering, Atg9 binding, and autophagic efficiency.

Diffusion Monte Carlo Study on Relative Stabilities of Boron Nitride Polymorphs

Although Boron nitride (BN) is a well-known compound widely used for engineering and scientific purposes, the phase stability of its polymorphs, one of its most fundamental properties, is still under debate. The ab initio determination of the ground state of the BN polymorphs, such as hexagonal and zinc-blende, is difficult because of the elusive Van der Waals interaction, which plays a decisive role in some of the polymorphs, making quantitative prediction highly challenging. Hence, despite multiple theoretical studies, there has been no consensus on the ground state yet, primarily due to contradicting reports. In this study, we apply a state-of-the-art ab initio framework - fixed-node diffusion Monte Carlo (FNDMC), to four well known BN polymorphs, namely hexagonal, rhombohedral, wurtzite, and zinc-blende BNs. Our FNDMC calculations show that hBN is thermodynamically the most stable among the four polymorphs at 0 K as well as at 300K. This result agrees with the experimental data of Corrigan~{\it et al.} and Fukunaga. The conclusions are consistent with those obtained using other high-level methods, such as coupled cluster. We demonstrate that the FNDMC is a powerful method to address polymorphs that exhibit bonds of various forms. It also provides valuable information, like reliable reference energies, when reliable experimental data are missing or difficult to access. Our findings should promote the application of FNDMC for other van der Waals materials.

Structure determination from unindexed powder data from scratch by a global optimization approach using pattern comparison based on cross-correlation functions.

A method of ab initio crystal structure determination from powder diffraction data for organic and metal-organic compounds, which does not require prior indexing of the powder pattern, has been developed. Only a reasonable molecular geometry is required, needing knowledge of neither unit-cell parameters nor space group. The structures are solved from scratch by a global fit to the powder data using the new program FIDEL-GO (`FIt with DEviating Lattice parameters - Global Optimization'). FIDEL-GO uses a similarity measure based on cross-correlation functions, which allows the comparison of simulated and experimental powder data even if the unit-cell parameters deviate strongly. The optimization starts from large sets of random structures in various space groups. The unit-cell parameters, molecular position and orientation, and selected internal degrees of freedom are fitted simultaneously to the powder pattern. The optimization proceeds in an elaborate multi-step procedure with built-in clustering of duplicate structures and iterative adaptation of parameter ranges. The best structures are selected for an automatic Rietveld refinement. Finally, a user-controlled Rietveld refinement is performed. The procedure aims for the analysis of a wide range of `problematic' powder patterns, in particular powders of low crystallinity. The method can also be used for the clustering and screening of a large number of possible structure candidates and other application scenarios. Examples are presented for structure determination from unindexed powder data of the previously unknown structures of the nanocrystalline phases of 4,11-difluoro-, 2,9-dichloro- and 2,9-dichloro-6,13-dihydro-quinacridone, which were solved from powder patterns with 14-20 peaks only, and of the coordination polymer dichloro-bis(pyridine-N)copper(II).

Synthesis, Crystal Structure, and Antibacterial Properties of Silver-Functionalized Low-Dimensional Layered Zirconium Phosphonates.

New insoluble layered zirconium phosphate carboxyaminophosphonates (ZPs), with the general formula Zr2(PO4)H5[(O3PCH2)2N(CH2)nCOO]2·mH2O (n = 3, 4, and 5), have been prepared and characterized. The crystal structure for n = 3 and 4 samples was determined ab initio from X-ray powder diffraction data. The structure for n = 3 was monoclinic in space group C2/c with the following unit cell parameters: a = 34.346(1) Å, b = 8.4930(2) Å, c = 9.0401(2) Å, and β = 97.15(1)°. The structure for n = 4 was triclinic in space group P1̅ with the following unit cell parameters: a = 17.9803(9) Å, b = 8.6066(4) Å, c = 9.0478(3) Å, α = 90.466(3)°, β = 94.910(4)°, and γ = 99.552(4)°. The two structures had the same connectivity as Zr phosphate glycine diphosphonate (n = 1), as previously reported. By intercalation of short amines, these layered compounds were exfoliated in single lamella or packets of a few lamellae, which formed colloidal dispersions in water. After a thorough characterization, the dispersed lamellae were functionalized with Ag nanoparticles, which were grown in situ on the surface of exfoliated lamellae. Finally, their antimicrobial activity was tested on several Gram-positive and Gram-negative bacteria. All of these systems were found to be active against the four pathogens most frequently isolated from orthopedic prosthetic infections and often causative of nosocomial infections. Interestingly, they were found to express powerful inhibitory activity even against bacterial strains exhibiting a relevant profile of antibiotic resistance such as Staphylococcus aureus ATCC 700699.

Entropy in Biochemical Failure

The ab-initio determination of the thermodynamic properties of the hydrolysis of the GTP gamma-phosphate in normal and abnormal cell functions of the RAS protein mutant Thr (Q61) leads to a description of energy cycle deviations in the abnormal mitogen-activated protein kinase cascade. 1 A predictive non-equilibrium probability statement describing the nonlinear changes for these open and finite-lifetime systems follows from reasonable enthalpy and entropy values between the normal and mutated forms based on structures of the GTPase states at the allosteric site. Recent advances in understanding entropy in terms of asymmetric and highly entropic catalysis lead to an investigation of the GTPase entropy, specifically with regard to a failure in catalysis of the phosphate fragment by a water hydrogen positioned by the enzyme. 2 Utilizing a simple atomic metal catalyst surface displacement model, a paradigm that reduces noise from the quantum entanglement plus atomic displacement terms results in the process entropy. The evaluation of entropies within the mixed ionic, covalent and entangled system requires a nonlinear Markovian approach utilizing von Neumann entropies achieved by a systematic accumulation of entangled potentials in a step-wise method. 3 , 4 Determination of the Hamiltonian for the entangled atomic state includes pure and mixed quantum states solved within the Araki–Leib triangle boundary resulting in only hard-entangled states, and the entanglement of Coulombic and Laughlin-like states can be evaluated by slicing the Hilbert spaces and solving the pure states, or mixed states separately, and then summing them. 5 Incorporating the resulting entanglement potentials as well as the Coulombic atomic displacement states into a derivative of the Fokker–Planck equation results in generated and produced entropy. 6

Theory of copper Kα and Kβ diagram lines, satellite spectra, and ab initio determination of single and double shake probabilities

High-accuracy MCDHF Cu Kα and Cu Kβ diagram spectra and major satellites are presented. Spectral eigenvalues reach a theoretical expansion convergence of 0.03 eV or 0.00025%, with gauge and amplitude convergence to 0.7% for Cu Kα diagram spectra. Dominant theoretical spectral eigenvalues are shown to be within 0.032 eV of experimental data. Ab initio shake-off contributions are presented in terms of total probability from each subshell and as separated single and double shake probabilities. Discrepancies between theory and experiment in copper X-ray spectra arise from profile asymmetries, relativistic terms and shake spectra not yet accounted for. These results and this improved agreement provide key fundamental parameters for processes towards XFEL evolution and resolving key discrepancies between theory and experiment.

Crystal Structures of Two Titanium Phosphate-Based Proton Conductors: Ab Initio Structure Solution and Materials Properties.

Transition-metal phosphates show a wide range of chemical compositions, variations of the valence states, and crystal structures. They are commercially used as solid-state catalysts, cathode materials in rechargeable batteries, or potential candidates for proton-exchange membranes in fuel cells. Here, we report on the successful ab initio structure determination of two novel titanium pyrophosphates, Ti(III)p and Ti(IV)p, from powder X-ray diffraction (PXRD) data. The low-symmetry space groups P21/c for Ti(III)p and P1̅ for Ti(IV)p required the combination of spectroscopic and diffraction techniques for structure determination. In Ti(III)p, trivalent titanium ions occupy the center of TiO6 polyhedra, coordinated by five pyrophosphate groups, one of them as a bidentate ligand. This secondary coordination causes the formation of one-dimensional six-membered ring channels with a diameter dmax of 3.93(2) Å, which is stabilized by NH4+ ions. Annealing Ti(III)p in inert atmospheres results in the formation of a new compound, denoted as Ti(IV)p. The structure of this compound shows a similar three-dimensional framework consisting of [PO4]3– tetrahedra and TiIV+O6 octahedra and an empty one-dimensional channel with a diameter dmax of 5.07(1) Å. The in situ PXRD of the transformation of Ti(III)p to Ti(IV)p reveals a two-step mechanism, i.e., the decomposition of NH4+ ions in a first step and subsequent structure relaxation. The specific proton conductivity and activation energy of the proton migration of Ti(III)p, governed by the Grotthus mechanism, belong to the highest and lowest, respectively, ever reported for this class of materials, which reveals its potential application in electrochemical devices like fuel cells and water electrolyzers in the intermediate temperature range.

A previously unknown cyclic alkanolamine and molecular ranking using the pair distribution function

A new six-membered cyclic alkanolamine with chemical formula C6H15N3O3 was synthesized by the reaction of glycolaldehyde with gaseous ammonia. The molecular structure, characterized by a hexagonal ring of alternating carbon and nitrogen atoms with three hydroxymethyl groups attached to the carbon atoms, could not be unambiguously determined by elemental analysis and 1H/13C/15N NMR. The molecular structure and conformation were further determined using a combination of vibrational spectroscopy (IR and Raman) and real-space pair distribution function (PDF) analysis. The crystal structure was determined ab initio from laboratory X-ray powder diffraction (XRPD) with orthorhombic space group Ama2 (No. 40) and unit-cell parameters a = 12.1054 (2) Å, b = 13.5537 (2) Å and c = 5.20741 (8) Å. Consistent structure models could be obtained by symmetry-independent PDF and PDF-Rietveld co-refinements. Independent local structure refinements indicate that the most likely deviations from the average structure consist of small tilting and translational distortions of hydrogen-bonded molecular stacks. Thermal analysis (TG/DTA) and temperature-dependent XRPD measurements were also performed to determine the thermal behavior.

Thermal and Tidal Evolution of Uranus with a Growing Frozen Core

Abstract The origin of the very low luminosity of Uranus is unknown, as is the source of the internal tidal dissipation required by the orbits of the Uranian moons. Models of the interior of Uranus often assume that it is inviscid throughout, but recent experiments show that this assumption may not be justified; most of the interior of Uranus lies below the freezing temperature of H2O. We find that the stable solid phase of H2O, which is superionic, has a large viscosity controlled by the crystalline oxygen sublattice. We examine the consequences of finite viscosity by combining ab initio determinations of the thermal conductivity and other material properties of superionic H2O with a thermal evolution model that accounts for heat trapped in the growing frozen core. The high viscosity provides a means of trapping heat in the deep interior while also providing a source of tidal dissipation. The frozen core grows with time because its outer boundary is governed by the freezing transition rather than compositional layering. We find that the presence of a growing frozen core explains the anomalously low heat flow of Uranus. Our thermal evolution model also predicts time-varying tidal dissipation that matches the requirements of the orbits of Miranda, Ariel, and Umbriel. We make predictions that are testable by future space missions, including the tidal Love number of Uranus and the current recessional rates of its moons.

Probing Molecular Motions in Metal-Organic Frameworks by Three-Dimensional Electron Diffraction.

Flexible metal–organic frameworks (MOFs) are known for their vast functional diversities and variable pore architectures. Dynamic motions or perturbations are among the highly desired flexibilities, which are key to guest diffusion processes. Therefore, probing such motions, especially at an atomic level, is crucial for revealing the unique properties and identifying the applications of MOFs. Nuclear magnetic resonance (NMR) and single-crystal X-ray diffraction (SCXRD) are the most important techniques to characterize molecular motions but require pure samples or large single crystals (>5 × 5 × 5 μm3), which are often inaccessible for MOF synthesis. Recent developments of three-dimensional electron diffraction (3D ED) have pushed the limits of single-crystal structural analysis. Accurate atomic information can be obtained by 3D ED from nanometer- and submicrometer-sized crystals and samples containing multiple phases. Here, we report the study of molecular motions by using the 3D ED method in MIL-140C and UiO-67, which are obtained as nanosized crystals coexisting in a mixture. In addition to an ab initio determination of their framework structures, we discovered that motions of the linker molecules could be revealed by observing the thermal ellipsoid models and analyzing the atomic anisotropic displacement parameters (ADPs) at room temperature (298 K) and cryogenic temperature (98 K). Interestingly, despite the same type of linker molecule occupying two symmetry-independent positions in MIL-140C, we observed significantly larger motions for the isolated linkers in comparison to those reinforced by π–π stacking. With an accuracy comparable to that of SCXRD, we show for the first time that 3D ED can be a powerful tool to investigate dynamics at an atomic level, which is particularly beneficial for nanocrystalline materials and/or phase mixtures.

Parton physics from a heavy-quark operator product expansion: Formalism and Wilson coefficients

Parton distribution functions (PDFs) and light-cone distribution amplitudes (LCDAs) are central non-perturbative objects of interest in high-energy inelastic and elastic scattering, respectively. As a result, an ab-initio determination of these objects is highly desirable. In this paper we present theoretical details for the calculation of the PDFs and LCDAs using a heavy-quark operator product expansion method. This strategy was proposed in a previous paper [Phys. Rev. D 73, 014501 (2006)] for computing higher moments of the PDFs using lattice QCD. Its central feature is the introduction of a fictitious, valence heavy quark. In the current article, we show that the operator product expansion (OPE) of the hadronic matrix element we study can also be expressed as the convolution of a perturbative matching kernel and the corresponding light-cone distribution, which in principle can be inverted to determine the parton momentum fraction dependence. Regarding the extraction of higher moments, this work also provides the one-loop Wilson coefficients in the OPE formulas for the unpolarized PDF, helicity PDF and pseudo-scalar meson LCDAs. Although these Wilson coefficients for the PDFs can be inferred from existing results in the literature, those for the LCDAs are new.

Ab initio structure determination of two new titanium phosphates synthesized via molten salt synthesis

<i>Ab initio</i> structure determination of two new titanium phosphates synthesized <i>via</i> molten salt synthesis

Ab initio DFT determination of structural, mechanical, optoelectronic, thermoelectric and thermodynamic properties of RbGeI3 inorganic perovskite for different exchange-correlation functionals

As a potential counterpart to the toxic CH3NH3PbI3 for photovoltaic applications, a lead-free non-toxic perovskite, rubidium germanium iodide (RbGeI3) is analyzed to assess its structural, mechanical, elastic, optoelectronic, thermoelectric and thermodynamic properties using the Full-Potential Augmented Plane Wave (FP-LAPW) approach of the WIEN2k code using density functional theory. Though various exchange correlation functionals viz. the Perdew Burke Ernzerhof scheme of Generalized Gradient Approximation (PBE-GGA), PBEsol, and WC-GGA are used, the TB-mBJ exchange correlation potential coupled with GGA, provides enhanced results. The lattice constants a0, bulk modulus B and its pressure derivative Bp are estimated to be 11.619096 bohr, 19.34 GPa and 5.4303 respectively with TB-mBJ exchange correlation potential. The elastic constants, C11, C12 and C44, Young’s modulus E, Shear modulus G, Poisson’s ratio ν and Anisotropic ratio A are estimated to be 43.4 GPa, 7.3 GPa, 7.9 GPa, 27.93 GPa, 11.09 GPa, 0.26 and 0.07 respectively using the Elastic 1.0 package. The density of states (DOS) and band structure are plotted for various exchange correlation functionals. The energy band gap and the absorption coefficient of the material, 1.338 eV and 10−3 cm−1 respectively, are found to be suitable for photovoltaic applications. Various thermoelectric coefficients like Seebeck coefficient, electrical conductivity and thermal conductivity are also calculated. The thermodynamic properties like Debye temperature, heat capacity, entropy and thermal expansion coefficient are plotted as a function of temperature and pressure using Gibbs2 program. The study indicates that inorganic cubic RbGeI3 has all the characteristics required as an absorber material for perovskite solar cells. However, the phonon dispersion spectrum shows the presence of imaginary modes indicating an instability in the structure with rise in temperature.

Retraction Notice: Ab initio structure determination and morphology study of La1.26 Zr0.25 Na2.5 N0.24 O2.54 triclinic structure from powder x-ray diffraction data

This paper deals with the ab initio structure determination of La1.26 N0.24 Na2.5 O2.54 Zr0.25 triclinic structure having triclinic crystal system via powder X-ray data using the Rietveld refinement method, and with physical properties characterization of a related solid solution at the room temperature structure of three compounds belonging to the Aurivillius family La1.26 N0.24 Na2.5 O2.54 Zr0.25 has been analyzed. La1.26 N0.24 Na2.5 O2.54 Zr0.25 crystallizes in a triclinic crystal system with P-1 space group. The starting material was Na2CO3,Zr(NO3)4 La2O3 for the Zr,La and Na analogues was derived from ab initio methods and refined using the Rietveld refinement method using JANA software package and visualization by Diamond computer program. The cations Na and La are disordered over the Zr sites while the La cation is found exclusively in the layers. The cell parameters are a=4.1040 A b=9.9102 A c=17.6117 A α=98.4299° β=93.4378° γ=92.2041°.The morphology and electrical properties are carried out of cited oxide.

Retraction Notice: Synthesis and ab initio Determination of Bi1.25 V0.123 Ca 0.245 N1.24 O8 cubic structure via powder X-ray diffraction data

This paper deals with the ab initio structure determination of Bi1.25 V0.123 Ca 0.245 N1.24 O8 cubic structure from powder X-ray data using the Rietveld method, and with physical properties characterization of a related solid solution. Bi1.25 V0.123 Ca 0.245 N 1.24 O 8 obtained from the annealing of a quenched cubic high temperature of sample, is cubic crystal system and lattice a=14.1243 A; Z =4. The structure refinement converged to Rp=0.018, R wp=0.0212 GOF=0.0102. The structure is built from cationic slabs parallel to (100) faces of the cubic cell. Each cell corresponds to one slab containing a mixed Bi1.25 V0.123 Ca 0.245 cationic layer (Bi(1)) sandwiched between two equivalent bismuth layers (Bi(2)). The cohesion of the cations in the slabs results from the presence of the oxygen atoms and nitrogen atoms distributed over three sites. Six O(1) and two O(2) atoms form a slightly distorted cubical polyhedron around the mixed cationic site (Bi(1)). (Bi(2)) atoms are surrounded by seven oxygen nitrogen atoms in a very distorted polyhedron. The important delocalization of (Bi(2)) lone pairs toward the integers spaces leads to significant bonds with the adjacent slabs and to the cohesion of the structure. Bi1.25 V0.123 Ca 0.245 O8 is the low symmetry variety of a particular sample of a wide solid solution domain that, formulated Bi1.25 V0.123 Ca0.245 O8, has been investigated. The formation of this phase from the irreversible transformation of quenched on heating and the subsequent transitions and non-transition metal oxides mixed valence have been evidenced by thermo diffractometry, conductivity measurements versus temperature, dilatometer, and thermal analyses. The morphological study was carried out by SEM.