Primitive Unit Cell Research Articles

Screening the organic materials database for superconducting metal-organic frameworks.

The increasing financial and environmental cost of many inorganic materials has motivated study into organic and "green" alternatives. However, most organic compounds contain a large number of atoms in the primitive unit cell, posing a significant barrier to high-throughput screening for functional properties. In this work, we attempt to overcome this challenge and identify superconducting candidates among the metal-organic-frameworks in the organic materials database using a recently proposed proxy for the electron-phonon coupling. We then isolate the most promising candidate for in-depth analysis, C9H8Mn2O11, providing evidence for superconductivity below 100mK.

Tutton salt (NH4)2Zn(SO4)2(H2O)6: thermostructural, spectroscopic, Hirshfeld surface, and DFT investigations

ContextAmmonium Tutton salts have been widely studied in recent years due to their thermostructural properties, which make them promising compounds for application in thermochemical energy storage devices. In this work, a detailed experimental study of the Tutton salt with the formula (NH4)2Zn(SO4)2(H2O)6 is carried out. Its structural, vibrational, and thermal properties are analyzed and discussed. Powder X-ray diffraction (PXRD) studies confirm that the compound crystallizes in a structure of a Tutton salt, with monoclinic symmetry and P21/a space group. The Hirshfeld surface analysis results indicate that the main contacts stabilizing the material crystal lattice are H···O/O···H, H···H, and O···O. In addition, a typical behavior of an insulating material is confirmed based on the electronic bandgap calculated from the band structure and experimental absorption coefficient. The Raman and infrared spectra calculated using DFT are in a good agreement with the respective experimental spectroscopic results. Thermal analysis in the range from 300 to 773 K reveals one exothermic and several endothermic events that are investigated using PXRD measurements as a function of temperature. With increasing temperature, two new structural phases are identified, one of which is resolved using the Le Bail method. Our findings suggest that the salt (NH4)2Zn(SO4)2(H2O)6 is a promising thermochemical material suitable for the development of heat storage systems, due to its low dehydration temperature (≈ 330 K), high enthalpy of dehydration (122.43 kJ/mol of H2O), and hydration after 24 h.MethodsComputational studies using Hirshfeld surfaces and void analysis are conducted to identify and quantify the intermolecular contacts occurring in the crystal structure. Furthermore, geometry optimization calculations are performed based on density functional theory (DFT) using the PBE functional and norm-conserving pseudopotentials implemented in the Cambridge Serial Total Energy Package (CASTEP). The primitive unit cell optimization was conducted using the Broyden–Fletcher–Goldfarb–Shanno (BFGS) algorithm. The electronic properties of band structure and density of states, and vibrational modes of the optimized crystal lattice are calculated and analyzed.Graphical abstract

Elastic wave control in reticulated plates using Schwarz primitive cells.

In this work, the Schwarz primitive unit cell is used as the building block of different types of metastructures for steering and focusing elastic vibrations. The emergence of a Bragg-type bandgap when constructing a two-dimensional plate from such unit cells is experimentally validated. It is demonstrated that increasing both mass and porosity of the Schwarz primitive leads to a decrease in the frequency of the out-of-plane propagating wave targeted in this study. By arranging these modified Schwarz primitive unit cells in constant and graded layouts, two-dimensional plates with an embedded metabarrier and a metalens are numerically designed. The metabarrier protects an interior area of the plate from the propagating waves on a wide frequency band (approx. 1.4-3.4 kHz). Equally, the refractive index profile necessary for gradient index lenses is obtained via a progressive variation of the added mass or, alternatively, the porosity of the unit cell over a rectangular area. For the first time, bending of the out-of-plane mode towards the focusing point is practically validated in a challenging mesoscale experiment requiring the assembly of different three-dimensional printed sections of the plate. The increased porosity design is advantageous not only in terms of overall lightweight, but also towards additive manufacturing as it requires less material.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 1)'.

First principles study of electronic structure of x-form phthalocyanine crystals doped with one-dimensional iodine atomic chains

The x-form phthalocyanine (Pc) crystal is composed of a square-lattice arrangement of one-dimensional and double-period molecular chains with molecular planes normal to the stacking direction, and doped iodine (I) atomic chains between these molecular chains are known to induce the insulator-metal transition. Using the van der Waals density functional method, we investigate the electronic structure of a single x-form silicon Pc (x-SiPc) chain and the x-SiPc crystal undoped and doped with I atomic chains in a comparative manner. Although a SiPc molecule has a Si pz derived orbital just above the LUMO, the aligned Si atoms in x-crystals, each of which is at the center of the molecular plane, dimerize in the stacking direction, which prevents formation of a Si metallic band. In a single SiPc chain, two molecules in each primitive unit cell are stacked face-to-face with a staggering angle of 45°. However, when these molecular chains aggregate to create x-crystals, the staggering angle deviates from 45° to about 40° to form H–H bonding orbitals like H2 molecules between neighboring molecular planes in the lateral direction. Doping of the I atomic chains converts half-filling of the doubly degenerate bands to a lower band occupancy, which corresponds to the insulator-metal transition observed experimentally. The equally spaced I atomic chains create a metallic band due to pz-orbital overlapping with an effective-mass ratio of 0.15. Although the SiPc chains operate to create equally spaced I atomic chains, the effect of I atoms trying to trimerize is larger. This trimerization prevents pz orbitals of I atoms from making a metallic band.

Symmetry-Guided Inverse Design of Self-Assembling Multiscale DNA Origami Tilings.

Recent advances enable the creation of nanoscale building blocks with complex geometries and interaction specificities for self-assembly. This nearly boundless design space necessitates design principles for defining the mutual interactions between multiple particle species to target a user-specified complex structure or pattern. In this article, we develop a symmetry-based method to generate the interaction matrices that specify the assembly of two-dimensional tilings, which we illustrate using equilateral triangles. By exploiting the allowed 2D symmetries, we develop an algorithmic approach by which any periodic 2D tiling can be generated from an arbitrarily large number of subunit species, notably addressing an unmet challenge of engineering 2D crystals with periodicities that can be arbitrarily larger than the subunit size. To demonstrate the utility of our design approach, we encode specific interactions between triangular subunits synthesized by DNA origami and show that we can guide their self-assembly into tilings with a wide variety of symmetries, using up to 12 unique species of triangles. By conjugating specific triangles with gold nanoparticles, we fabricate gold-nanoparticle supracrystals whose lattice parameter spans up to 300 nm. Finally, to generate economical design rules, we compare the design economy of various tilings. In particular, we show that (1) higher symmetries allow assembly of larger unit cells with fewer subunits and (2) linear supracrystals can be designed more economically using linear primitive unit cells. This work provides a simple algorithmic approach to designing periodic assemblies, aiding in the multiscale assembly of supracrystals of nanostructured "meta-atoms" with engineered plasmonic functions.

Enhancing mechanical properties and damage tolerance of additive manufactured ceramic TPMS lattices by hybrid design

AbstractMany studies have reported that additive manufactured ceramic lattices with microarchitectures often exhibit low‐strain brittle fracture behavior. In this work, the fracture behavior of ceramic triply periodic minimal surface (TPMS) lattices was optimized by introducing a hybrid design strategy that utilizes different microarchitectures. Hybrid ceramic TPMS structures incorporating Gyroid and Primitive unit cells were successfully fabricated using the Lithography‐based ceramics manufacturing (LCM) technique, and their mechanical properties were evaluated under both quasistatic and dynamic compression. The hybrid designs exhibited improved damage tolerance and fracture strength compared to their normal counterparts. Compared to normal Gyroid and Primitive structures, the G2P2 structure exhibits the best energy absorption capacity of 12.5 × 104 J/m3, demonstrating a 13% and 217% increase in energy absorption capacity under quasistatic loading, respectively. Additionally, compared with other normal and hybrid designs, the G2P2 structure exhibits the highest fracture strength of 13.03 MPa under quasistatic loading conditions. Moreover, the P2G hybrid structure displayed a distinct deformation pattern characterized by a smoother stress decrease under quasistatic loading, enhancing damage tolerance. The order of Young's modulus under quasistatic loading was Normal Gyroid ≈ G2P2 > G2P1 > Normal Primitive > P2G. Fracture strength follows the order of G2P2 ≈ Normal Gyroid > Normal Primitive > G2P1 > P2G. The mechanical properties of hybrid TPMS structures suggest that the hybrid design strategy can broaden the achievable range of mechanical properties among ceramic TPMS structures.

Multifunctional Design of Triply Periodic Minimal Surface Structures for Temporary Pediatric Fixation Devices

Fracture fixation and limb deformity correction in pediatric orthopedics often use temporary metallic fixation devices. These devices’ higher stiffness compared to cortical bone leads to stress shielding, causing significant bone density reduction, periprosthetic loosening, and bone growth interference. The 3D‐printed triply periodic minimal surface (TPMS) structures present a promising engineering solution to match bone stiffness while ensuring reliable implant strength. In this study, finite‐element modeling and experimental testing are employed to identify optimal multifunctional TPMS‐based lattices that meet the required design constraints of 1) stiffness in the range of cortical bone, 2) strength in the range of cortical bone, 3) minimum osteointegration to facilitate the implant removal after healing, and 4) manufacturability with limited defect sensitivity. Six different types of TPMS structures in Ti–6Al–4V material manufactured via laser powder bed fusion are evaluated for their ability to target the lower and upper bounds of pediatric cortical bone stiffness. Lattices based on the Primitive unit cell design are superior, demonstrating the highest strength/stiffness ratio, best manufacturability, and potentially reduced osteointegration due to larger pore size, smaller surface area, and smallest negative Gaussian curvature compared to other investigated TPMS types.

A novel analytical solution for determining the shear behavior of the lattice structure based on the Primitive unit cell considering the shear and bending effect

The lattice structure of Schwarz Primitive triply periodic minimal surfaces (P-TPMS) has recently attracted significant attention. This attention arises from its unique topological configuration and superior mechanical properties. This paper studied the effect of changing geometric parameters and the effect of the number of unit cells on the shear modulus of the P-TPMS structure. An analytical model considering the shear and bending effects was derived for the first time, which can efficiently and accurately determine the shear modulus of the P-TPMS lattice structure. Shear modulus was obtained for relative densities in the range of 0.24–0.76. The relative density was calculated by considering the geometric parameter of the surface size (k). The analytical expression was verified by carrying out finite element simulations. Based on the results of this investigation, the shear modulus of the Primitive unit cell changes significantly with different surface size values. Specifically, at k = 0.35, the normalized shear modulus value is 24 times greater than at k = 0.65. This characteristic of the Primitive unit cell extends the range of choices for designers. The completed Ashby diagram suggests that lattice structures based on Primitive unit cells could be one of the most appropriate choices for achieving high shear modulus compared to other structures.

Revealing the spatial nature of sublattice symmetry

The sublattice symmetry on a bipartite lattice is commonly regarded as the chiral symmetry in the AIII class of the tenfold Altland–Zirnbauer classification. Here, we reveal the spatial nature of sublattice symmetry and show that this assertion holds only if the periodicity of primitive unit cells agrees with that of the sublattice labeling. In cases where the periodicity does not agree, sublattice symmetry is represented as a glide reflection in energy–momentum space, which inverts energy and simultaneously translates some k by π, leading to substantially different physics. Particularly, it introduces novel constraints on zero modes in semimetals and completely alters the classification table of topological insulators compared to class AIII. Notably, the dimensions corresponding to trivial and nontrivial classifications are switched, and the nontrivial classification becomes Z2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${{\\mathbb{Z}}}_{2}$$\\end{document} instead of Z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mathbb{Z}}$$\\end{document}. We have applied these results to several models, including the Hofstadter model both with and without dimerization.

Restoration of non-Hermitian bulk-boundary correspondence by counterbalancing skin effect

In systems exhibiting the non-Hermitian skin effect (NHSE), the bulk spectrum under open boundary conditions (OBC) significantly differs from that of its periodic counterpart. This disparity renders the conventional bulk-boundary correspondence (BBC) inapplicable. Here we propose an intuitive approach called doubling and swapping to restore the BBC, using the non-Hermitian Su-Schrieffer-Heeger model as an example. Explicitly, we construct a modified system free of NHSE by swapping the asymmetric intracell hoppings in every second primitive unit cell. Importantly, this change does not alter the OBC spectrum. As a result, the modified periodic system can serve as the bulk for defining topological invariants that accurately predict edge states and topological phase transitions. The basic principle is applicable to many other systems. By extending the study to disordered systems in which the asymmetric hoppings are randomly swapped, we show that two types of winding numbers can also be defined to account for the NHSE and topological edge states, respectively.

Controllable magnetic ground states in metal diiodide MI2 (M: Fe, Co, and Ni) monolayers by electric field

We investigated the controllable magnetic ground states of 1T metal diiodide MI2 (M: Fe, Co, and Ni) monolayers by applying the electric field. To do so, we utilized the generalized Bloch theorem within the density functional theory on the primitive unit cell to examine the appearance of three possible magnetic ground states, namely, ferromagnetic, spiral, and antiferromagnetic states from the specified spiral vector. We found that the ground state can be changed as the electric field increases but depends on the lattice parameter. In general, the spiral ground state exists as the electric field is taken into account, thus all these materials are prominent as multiferroics. Also, based on the competition between ferromagnetic and antiferromagnetic exchange interactions, we observed that for FeI2, the transition from the ferromagnetic exchange to the antiferromagnetic exchange happens as the electric field increases, while CoI2 and NiI2 tend to preserve their original exchange interaction. This implies that only the magnetic state in FeI2 sensitively depends on the electric field.

Design of second-order phoxonic topological insulators with customized bandgaps

Second-order phononic and photonic topological insulators hosting topologically protected edge and corner states provide opportunities for the robust manipulation of elastic/acoustic and electromagnetic (EM) waves, respectively. Despite their potential, the development of second-order phoxonic topological insulators, which combine functionalities of second-order phononic and photonic topological insulators, remains largely unexplored. Herein, we design second-order phoxonic topological insulators (SPTI) with customized bandgaps. An inverse design approach is proposed to engineer phoxonic crystals (PCs) featuring customized odd-order phononic and photonic bandgaps simultaneously. Topological phase transition is induced by translating the primitive unit cell (UC) of the inverse-designed PC with half of the lattice constant horizontally and vertically. Thereafter, the SPTI is constructed by juxtaposing the primitive and translated UCs to form a corner between them. Multiple SPTIs, capable of manipulating both acoustic and EM waves, as well as those governing elastic and EM waves, are created. Our work paves the way for customized SPTIs with tailored bandgaps to support diverse phononic and photonic corner states. Meanwhile, the designed SPTIs also provide a platform to design the higher-order topological optomechanical devices.

Unraveling the connection of electronic and phononic structure with mechanical properties of commercial AZ80 alloy

Magnesium alloys, particularly in the aluminum-zinc (AZ) series, are widely recognized for their remarkable strength-to-weight ratio. We performed electronic structure, lattice dynamics, and mechanical properties of the AZ80 alloy using first-principles density-functional theory. The influence of dilute alloying by Al/Zn was observed in electronic-structure of AZ80 through hybridization of Mg-(s,p) with Al-p/Zn-d states. The Allen’s electronegativity difference between Mg and Al/Zn was found to induce charge transfer mechanism that provides solid-solution strengthening and ductility, in agreement with experiments. The electronic and phononic band-structure was unfolded onto the primitive unit cell of pure Mg to provide key information related to structural distortions and disorder effects. Finally, the dynamic and mechanical stability of AZ80 were confirmed by phonons and Born-Huang criteria, respectively. Collectively, this study provides valuable insights into the fundamental properties of lightweight commercial grade AZ80, essential for application-oriented design of Mg alloys.

The rule of four: anomalous distributions in the stoichiometries of inorganic compounds

Why are materials with specific characteristics more abundant than others? This is a fundamental question in materials science and one that is traditionally difficult to tackle, given the vastness of compositional and configurational space. We highlight here the anomalous abundance of inorganic compounds whose primitive unit cell contains a number of atoms that is a multiple of four. This occurrence—named here the rule of four—has to our knowledge not previously been reported or studied. Here, we first highlight the rule’s existence, especially notable when restricting oneself to experimentally known compounds, and explore its possible relationship with established descriptors of crystal structures, from symmetries to energies. We then investigate this relative abundance by looking at structural descriptors, both of global (packing configurations) and local (the smooth overlap of atomic positions) nature. Contrary to intuition, the overabundance does not correlate with low-energy or high-symmetry structures; in fact, structures which obey the rule of four are characterized by low symmetries and loosely packed arrangements maximizing the free volume. We are able to correlate this abundance with local structural symmetries, and visualize the results using a hybrid supervised-unsupervised machine learning method.

A comprehensive investigation of the lattice structure mechanical properties based on Schwarz Primitive triply periodic minimal surface: Elastic modulus, yield strength, and maximum bearing force in the elastic region

Due to ongoing investigations, the potential for using triply periodic minimal surface (TPMS) lattice structures in various industries has been increased. The analytical relationships that determine the mechanical properties of these structures make cost-effective designs achievable for designers. In this study, a comprehensive investigation that includes analytical, numerical, and experimental approaches to determine the mechanical properties of the Primitive triply periodic minimal surface (P-TPMS) lattice structure under unidirectional loading was performed. The innovation of this paper is the derivation of analytical relationships of mechanical properties, including elastic modulus, yield strength, and maximum load-bearing force in the elastic region in terms of geometrical parameters of Primitive unit cell and properties of the constituent materials. These mechanical properties were obtained using the energy method and Euler-Bernoulli beam theory for relative densities in the range of 0.24–0.76. Relative density was determined based on the geometric parameter of the surface size (m). In addition, the lattice structures were fabricated additively manufactured, and compressive test experiments were conducted. The mechanical properties of P-TPMS lattice structures vary dramatically with varying surface size values, according to the study's findings. The P-TPMS lattice structure's elastic modulus and yield strength at m=0.35 are more than 11 and 32 times larger, respectively than the yield stress and elastic modulus at m=0.65. The unit cell's length has no bearing on the elastic modulus or yield strength.

Carbon contamination of elemental beta-boron promoted a stable boron carbide by spark plasma sintering

The effect of carbon contamination on the elemental beta boron (β-B) from the graphite components of spark plasma sintering (SPS) was investigated. The X-ray diffraction, analytical electron microscopy (AEM) and Raman spectroscopy witnessed boron carbide (B13+xC2-x where x=0.05–0.35), when SPS temperature was above 1750 °C. The degree of carbon contamination became severe with increasing SPS temperature to 1800 °C and 1850 °C and formed a single-phase rhombohedral boron carbide with about 12 wt% of carbon. Our observations indicate that the carbon gets kinetically trapped into β-B to form boron carbide with a primitive unit cell consisting mainly of icosahedral B11C and three-atom chain of CBB configurations. After 6 months of natural aging, it has been revealed that boron carbide formed at and below sintering temperatures of 1800 °C is not a thermodynamically stable phase, and transformed reversibly to β-B structure. X-ray photoelectron spectroscopy ascertained that there are no longer B-C bonds and the existence of more CC bonds in a 6 months aged specimen, suggesting carbon is no longer strongly bonded to boron, but precipitates as graphitic structure. Further examination using atom probe tomography and AEM confirmed the existence of carbon nanoclusters within grains and high concentration of carbon segregating onto grain boundaries. The phase transformation of boron carbide to mostly boron resulted in a significant loss of hardness and modulus in a bulk SPS specimen. This study underscores the importance of solid solution and local bonding environment in icosahedral boron-rich solids for phase stability and sustained properties.

Understanding layered compounds under high pressure

This Tutorial focuses on the physics of layered compounds under high pressure. We have chosen h-BN and III–VI layered materials as representative materials. h-BN layers are strictly two-dimensional. Layers in III–VI compounds are more complex, and subtle details in their structural behavior play an important role in the evolution of high pressure properties. They are also interesting because they contain a different number of layers in their primitive unit cell and/or have a different ionic character. We begin describing the structural evolution. We discuss the experimental challenges encountered as well as the main findings related to intra- and interlayer compressibility, polytype influence, and geometrical modifications induced by pressure inside the layers. We then describe lattice vibrations. The origin of the modes is reviewed, paying attention to the relationships between atom motions in different layers. We discuss the convenience of redefining the Grüneisen parameter and describe the behavior of rigid layer modes, soft modes, and Davidov pairs. The last section is devoted to the electronic properties. We show that the changes observed when passing from a single layer to a three-dimensional BN are qualitatively similar to those induced by high pressure. The pressure behavior of electronic transitions in III–VI layered compounds is very rich, revealing the subtle balance between intra- and inter-layer interactions. Finally, we take advantage of high pressure studies to explain the formation of the Mexican hat type of valence band at ambient conditions in single layers of InSe and GaSe, but not in three-dimensional compounds.

Distinct vibrational signatures and complex phase behavior in metallic oxygen

Evidence for metallization in dense oxygen has been reported for over 30 years [Desgreniers et al., J. Phys. Chem. 94, 1117 (1990)] at a now routinely accessible 95 GPa [Shimizu et al., Nature 393, 767 (1998)]. However, despite the longevity of this result and the technological advances since, the nature of the metallic phase remains poorly constrained [Akahama et al., Phys. Rev. Lett. 74, 4690 (1995); Goncharov et al., Phys. Rev. B 68, 224108 (2003); Ma, Phys. Rev. B 76, 064101 (2007); and Weck et al., Phys. Rev. Lett. 102, 255503 (2009)]. In this work, through Raman spectroscopy, we report the distinct vibrational characteristics of metallic ζ-O2 from 85 to 225 GPa. In comparison with numerical simulations, we find reasonable agreement with the C2/m candidate structure up to about 150 GPa. At higher pressures, the C2/m structure is found to be unstable and incompatible with experimental observations. Alternative candidate structures, C2/c and Ci, with only two molecules in the primitive unit cell, are found to be stable and more compatible with measurements above 175 GPa, indicative of the dissociation of (O2)4 units. Further, we report and discuss a strong hysteresis and metastability with the precursory phase ϵ-O2. These findings will reinvigorate experimental and theoretical work into the dense oxygen system, which will have importance for oxygen-bearing chemistry, prevalent in the deep Earth, as well as fundamental physics.

Optimising degradation and mechanical performance of additively manufactured biodegradable Fe–Mn scaffolds using design strategies based on triply periodic minimal surfaces

Additively manufactured lattices based on triply periodic minimal surfaces (TPMS) have attracted significant research interest from the medical industry due to their good mechanical and biomorphic properties. However, most studies have focussed on permanent metallic implants, while very little work has been undertaken on manufacturing biodegradable metal lattices. In this study, the mechanical properties and in vitro corrosion of selective laser melted Fe–35%Mn lattices based on gyroid, diamond and Schwarz primitive unit-cells were comprehensively evaluated to investigate the relationships between lattice type and implant performance. The gyroid-based lattices were the most readily processable scaffold design for controllable porosity and matching the CAD design. Mechanical properties were influenced by lattice geometry and pore volume. The Schwarz lattices were stronger and stiffer than other designs with the 42% porosity scaffold exhibiting the highest combination of strength and ductility, while diamond and gyroid based scaffolds had lower strength and stiffness and were more plastically compliant. The corrosion behaviour was strongly influenced by porosity, and moderately influenced by geometry and geometry-porosity interaction. At 60% porosity, the diamond lattice displayed the highest degradation rate due to an inherently high surface area-to-volume ratio. The biodegradable Fe–35Mn porous scaffolds showed a good cytocompatibility to primary human osteoblasts cells. Additive manufacturing of biodegradable Fe–Mn alloys employing TPMS lattice designs is a viable approach to optimise and customise the mechanical properties and degradation response of resorbable implants toward specific clinical applications for hard tissue orthopaedic repair.

Synthesis, crystal structure and thermal behavior of tetra-kis-(3-cyano-pyridine N-oxide-κO)bis-(thio-cyanato-κN)cobalt(II), which shows strong pseudo-symmetry.

The title compound, [Co(SCN)2(C6H4N2O)4], was prepared by the reaction of cobalt(II)thio-cyanate with 3-cyano-pyridine N-oxide in ethanol. In the crystal, the cobalt(II) cations are octa-hedrally coordinated by two terminal N-bonded thio-cyanate anions and four O-bonded 3-cyano-pyridine N-oxide coligands, forming discrete complexes that are located on centers of inversion, hence forming trans-CoN2O4 octa-hedra. The structure refinement was performed in the monoclinic space group P21/n, for which a potential lattice translation and new symmetry elements with a fit of 100% is suggested. The structure can easily be refined in the space group I2/m, where the complexes have 2/m symmetry. However, nearly all of the reflections that violate the centering are observed with significant intensity and the refinement in P21/n leads to significantly lower R(F) values (0.027 versus 0.033). Moreover, in I2/m much larger components of the anisotropic displacement parameters are observed and therefore, the crystal structure is presented in the primitive unit cell. IR investigations confirm that the anionic ligands are only terminally bonded and that the cyano group is not involved in the metal coordination. PXRD investigations show that a pure crystalline phase has been obtained and measurements using simultaneously thermogravimetry and differential thermoanalysis reveal that the compound decomposes in an exothermic reaction upon heating, without the formation of a coligand-deficient inter-mediate phase.