Higher Coordination Number Research Articles

Formation mechanism of Al2O3‐YAG amorphous ceramic coating deposited via atmospheric plasma spraying

AbstractAl2O3‐YAG (Al5Y3O12) amorphous ceramic coatings exhibit excellent crack propagation resistance under harsh wear services due to the amorphous phase contributing to the plastic deformation performance of the coating. However, the formation mechanism of the amorphous phase is ambiguous. This study mainly investigated the formation mechanism of Al2O3‐YAG amorphous coating prepared by atmospheric plasma spraying from the perspective of crystallization chemistry. Nano and microsized powders with low eutectic point ratio were selected as feedstock for comparison. X‐ray diffraction, scanning electron microscope, and electron backscattered diffraction were used to analyze the phase composition, morphologies, phase distribution, and structure of the coating. It is concluded that the significant thermodynamically stable structure of polycompound with high coordination numbers of cations prioritized crystallizing in the Al2O3‐YAG melt, but it needed more time to crystallize and hardly crystallized in the limited time during plasma spraying. Therefore, the selection of as‐sprayable powder should also be considered the critical factor for preparing amorphous coatings. The nanoscale or submicro scale powder distributed uniformly with low eutectic point ratio was chosen as the feedstock to ensure the powder droplets diffuse sufficiently during deposition.

Boosting Activity and Stability of Metal Single-Atom Catalysts via Regulation of Coordination Number and Local Composition.

Controlling the chemical environments of the active metal atom including both coordination number (CN) and local composition (LC) is vital to achieve active and stable single-atom catalysts (SACs), but remains challenging. Here we synthesized a series of supported Pt1 SACs by depositing Pt atoms onto the pretuned anchoring sites on nitrogen-doped carbon using atomic layer deposition. In hydrogenation of para-chloronitrobenzene, the Pt1 SAC with a higher CN about four but less pyridinic nitrogen (Npyri) content exhibits a remarkably high activity along with superior recyclability compared to those with lower CNs and more Npyri. Theoretical calculations reveal that the four-coordinated Pt1 atoms with about 1 eV lower formation energy are more resistant to agglomerations than the three-coordinated ones. Composition-wise decrease of the Pt-Npyri bond upshifts gradually the Pt-5d center, and minimal one Pt-Npyri bond features a high-lying Pt-5d state that largely facilitates H2 dissociation, boosting hydrogenation activity remarkably.

Ionic Liquid for Perovskite Solar Cells: An Emerging Solvent Engineering Technology

ConspectusPerovskite solar cells (PSCs) have, in recent years, become one of the most in-depth photovoltaic materials in many different disciplines due to their long-range charge carrier diffusion lengths, strong light absorption, easy tuning of the band gaps, low defect density, and solution processability. The power conversion efficiency (PCE) of single-junction PSCs has reached a certified value of 25.5%, which has caught up with or even surpassed traditional photovoltaic technologies, such as silicon (Si) solar cells, thin film solar cell, etc. In addition to the performance of PSCs comparable to traditional photovoltaic technology, its biggest feature is that it can be prepared by a solution method. The preparation process of the solution method simplify the film preparation process and greatly reduce the preparation cost. In addition, the solution method provides a favorable option for the energy supply of flexible wearable devices in the future.At present, the preparation of PSCs mainly uses organic molecular solvents, including N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), and their mixed solvents. However, most of these commonly used organic solvents are unsafe and are likely to cause water and soil pollution, harm to the human body, and safety accidents. In addition, most solvents have a high coordination number, which limits the crystallization of perovskite. Furthermore, high-quality perovskite films require the introduction of a large amount of high boiling point, polar and aprotic antisolvents to assist crystallization, such as chlorobenzene, ether, and ethyl acetate. In addition to the toxicological problems of the antisolvent, the technology has a relatively narrow operating time window, relatively high operating environment requirements, and relatively low repeatability, which greatly limits the large-scale production of PSCs. Therefore, It is very necessary to develop a new solvent engineering technology for PSCs, which is green and pollution-free, is a simple process, and has high efficiency, long-term stability, and low cost. Recently, we have developed a series of ionic liquids, including MAAc, MAFa, BAAc, etc., which can be used as solvents to prepare efficient and stable PSCs. It allows the production of smooth and continuous polycrystalline perovskite thin films in ambient air through a simple spin coating methodIn this Account, we started with the discovery of ionic liquids as solvents to PSCs. We have proposed new strategies for improving and enhancing ionic liquid-based PSCs, including interface engineering, solvent engineering, and additive engineering. Furthermore, the stable and efficient mechanism of ionic liquid-based perovskite solar cells has been revealed. In view of the designable characteristics of ionic liquids, some functional ionic liquids have been designed and applied to different systems of halide perovskites, which has important guiding significance for the development of more functional ionic liquids for PSCs. Finally, the challenges and future directions of ionic liquid-based PSCs from both large-scale production and technological perspectives are proposed to provide a new method for the commercialization of PSCs.

Fine property-tuning through Ca content control in a facile synthesis of glasses-based self-setting injectable hydrogel

Self-setting injectable composite hydrogels are promising materials in tissue engineering. In this study a facile synthetic approach was designed based on traditional sol–gel method to produce particulate calcium aluminosilicate-type glasses, which were then formulated with potassium alginate to form a self-setting injectable hydrogel. In order to control the setting-time and mechanical properties of the composite materials, a series of samples were produced with different starting chemical composition. The change in chemical composition and morphology of the glass particles in response to varying initial Ca2+ content were further elucidated by a combination of EM, XRF and NMR spectroscopy, revealing that the binary aluminosilicate glass was preferably formed when low Ca content (<20%) was used in the formulation. At higher Ca content (>30%), calcium aluminosilicates were predominantly formed due to the change in the type of zeolite precursor formed during the low temperature nucleation process in the sol–gel approach. It was also found the hardening times of the alginate gels was positively correlated to the mole ratio of Ca/Al due to high acid resistance of high coordination number Al species. For hydrogels made with glass particle additions, the mechanical strengths were also positively correlated with the Ca/Al ratio for all formulations.

Theoretical investigation of hydrated [Lu(OH)2]+ adsorption on kaolinite(0 0 1) surface with DFT calculations

Kaolinite is a major mineral present in ion-adsorption rare earth ores, which are the primary source of lutetium (Lu). In those ores, Lu is mainly found to be adsorbed on the kaolinite surface in the form of hydrated or hydroxyl-hydrated ions, and can therefore be desorbed by ion-exchange leaching. This study used density functional theory calculations to investigate the adsorption mechanisms and bonding nature of hydrated [Lu(OH)2]+ ions on the kaolinite (0 0 1) surface. Lu3+ exhibited directed tendency geometry with high coordination number of nine. [Lu(OH)2(H2O)6]+, the most stable ion in aqueous system, was considered as the initial structure for the adsorption models. To investigate bonding between hydrated [Lu(OH)2]+ and the kaolinite surface, outer-layer (related to hydrogen bonding) and inner-layer (related to coordination bonding) adsorption models were applied. The surface charge and HOMO distribution of the deprotonated Al-OH surface were also investigated. Owing to the high reactivity of the deprotonated hydroxyls, inner-layer adsorption was dominated by coordination bonds between Lu and surface oxygen, with bidentate complexation at Ol site giving the largest adsorption energy (-663.86 kJ/mol). Moreover, partial density of state projections and Mulliken bond populations showed that the antibonding combination of Lu 5d and Os 2p is the dominant orbital contribution of Lu and surface oxygen. These insights into the Lu adsorption mechanism can aid in developing improved ion-exchange leaching techniques.

The angular overlap model of ligand field theory for f elements: An intuitive approach building bridges between theory and experiment

Lanthanoid ions are well-known for their characteristic optical and magnetic properties interesting for a wide range of applications. Most of these properties show a subtle dependence on the surrounding ligands. Unlike the transition metal ions with their often encountered octahedral or tetrahedral coordination in compounds, rare earth ions are typically found in coordination geometries with low symmetries and high coordination numbers. The quantitative treatment of the ligand field in the so-called Wybourne scheme then becomes overparametrized and not readily insightful but merely a technical tool. In this review, we want to present the alternative approach by the chemically intuitive angular overlap model (AOM) of ligand field theory that is independent from symmetry and allows to decompose any coordination geometry into its separate metal–ligand bonds with well-known bonding character. It is the goal of this review to demonstrate its strength in the semi-quantitative description of opto-magnetic properties of the rare earth ions on carefully selected examples from practice. Finally, we compare the AOM to conventional Wybourne-parametrized ligand field theory and show how the two schemes of ligand field theory are related to one another. Overall, this review offers a perspective on future approaches to ligand field calculations with f elements with the benefit of full transparency and intuitive understanding rather than technical fitting.

From Chemical Curiosities and Trophy Molecules to Uranium-Based Catalysis: Developments for Uranium Catalysis as a New Facet in Molecular Uranium Chemistry.

Catalysis remains one of the final frontiers in molecular uranium chemistry. Depleted uranium is mildly radioactive, continuously generated in large quantities from the production and consumption of nuclear fuels and accessible through the regeneration of “uranium waste”. Organometallic complexes of uranium possess a number of properties that are appealing for applications in homogeneous catalysis. Uranium exists in a wide range of oxidation states, and its large ionic radii support chelating ligands with high coordination numbers resulting in increased complex stability. Its position within the actinide series allows it to involve its f-orbitals in partial covalent bonding; yet, the U–L bonds remain highly polarized. This causes these bonds to be reactive and, with few exceptions, relatively weak, allowing for high substrate on/off rates. Thus, it is reasonable that uranium could be considered as a source of metal catalysts. Accordingly, uranium complexes in oxidation states +4, +5, and +6 have been studied extensively as catalysts in sigma-bond metathesis reactions, with a body of literature spanning the past 40 years. High-valent species have been documented to perform a wide variety of reactions, including oligomerization, hydrogenation, and hydrosilylation. Concurrently, electron-rich uranium complexes in oxidation states +2 and +3 have been proven capable of performing reductive small molecule activation of N2, CO2, CO, and H2O. Hence, uranium’s ability to activate small molecules of biological and industrial relevance is particularly pertinent when looking toward a sustainable future, especially due to its promising ability to generate ammonia, molecular hydrogen, and liquid hydrocarbons, though the advance of catalysis in these areas is in the early stages of development. In this Perspective, we will look at the challenges associated with the advance of new uranium catalysts, the tools produced to combat these challenges, the triumphs in achieving uranium catalysis, and our future outlook on the topic.

Amorphous Alloys Atomic Structure Investigation by Means of Electron Microscopy and Diffraction

In the paper, the atomic structure of amorphous and nanocrystalline alloys of the electrolytically obtained CoP, NiP, CoNiP, CoW, and CoNiW systems has been studied. The structure was investigated by electron microscopy and diffraction using a Libra 200 HR FE transmission electron microscope at an accelerating voltage of 200 kV within a temperature range of 50-35 °C. The obtained radial atom distribution function and the coordination sphere radii are in good agreement with the data for the cobalt structure in the cubic and hexagonal modifications. The high coordination numbers of the third and fourth coordination spheres allow suggesting a predominantly cubic structure of the local atom environment in CoP samples but somewhat lower, which is explained by the presence of free volume and phosphorus atoms distorting the local structure. When heating, the near atomic order also corresponds to the cubic phase of cobalt, and the ordering occurs in the second, third, and fourth coordination spheres. The data obtained for CoNiP alloys indicate that by configuration, the local atomic environment is closer to the hexagonal structure of nickel. In general, the structure of the CoP-CoNiP system alloy films obtained by electrolytic deposition is already in one of the local minima of the total system energy, which is confirmed by the near atomic order similar to the cubic phase of cobalt or hexagonal phase of nickel. This determines the good stability of the structure and properties during thermal exposure.

High Thermal Stability and Fast Speed Phase Change Memory by Optimizing GeTe Alloys with Ru Doping

Phase change memory (PCM) has obvious advantages in reading, writing, fatigue characteristics and other characteristics, which make it can be a universal memory. At the same time, as a storage-level memory, PCM technology is expected to change the computer architecture and realize the integration of storage and calculation. In this paper, Ru6.8Ge50Te50 is proposed for PCM, which has achieved 144.9 °C data retention for 10 years, 6 ns operation speed. The high data retention of the phase change material is mainly due to the high coordination number of Ru and its strong bonding with Ge and Te atoms in the amorphous phase, thus enhancing the robustness of the atomic matrix. The amorphous structure model is calculated through molecular dynamics melting-quenching process, which shows that a relatively uniform amorphous phase is obtained by Ru doping. These findings proved that Ru6.8Ge50Te50 can be used as a candidate storage material for PCM.

Ultrahigh Proton Conduction via Extended Hydrogen-Bonding Network in a Preyssler-Type Polyoxometalate-Based Framework Functionalized with a Lanthanide Ion.

The exploration of composition-structure-function relationship in proton-conducting solids remains a challenge in materials chemistry. Polyoxometalate-based compounds have been long considered as candidates for proton conductors; however, their low structural stability and a large decrease in conductivity under reduced relative humidity (RH) have limited their applications. To overcome such limitations, the hybridization of polyoxometalates with proton-conducting polymers has emerged as a promising method. Besides, 4f lanthanide ions possess a high coordination number, which can be utilized to attract water molecules and to build robust frameworks. Herein, a Preyssler-type polyoxometalate functionalized with a 9-coordinate Eu3+ (Eu[P5W30O110K]11-) is newly synthesized and combined with poly(allylamine) with amine moieties as protonation sites. The resulting robust crystalline composite exhibits an ultrahigh proton conductivity >10-2 S cm-1 at 368 K and 90% RH, which is still >10-3 S cm-1 at 50% RH, due to the strengthened and extended hydrogen-bonding network.

Metal Organic Framework in Membrane Separation for Wastewater Treatment: Potential and Way Forward

Metal organic framework (MOF) is a class of porous material that has been acknowledged for its high porosity, tunable pores and distinctive chemical functionalities. This paper reviewed some of the selected MOF applied in adsorption and membrane separation for wastewater treatment. As adsorbent, certain MOF demonstrated high solute rejection and adsorption capacity, much contributed by high surface area and more active sites to bind with solutes. In another way, MOF can be incorporated as nanofiller in thin-film nanocomposite or mixed-matrix membrane. This water stable MOF inclusion has tuned the membrane chemistry and morphology to be more selective toward solute while enhancing water permeability. The stability of MOF was governed by high number of positive charge per atom, high coordination number, presence of hydrophobic functional groups and also their ability to resist coordination with water molecules. Important issues regarding with MOF in membrane had been addressed, particularly MOF agglomeration that further deteriorated membrane performance. At the end of the review, a conclusion and future perspective is suggested as remarks.

Metavalent Bonding in GeSe Leads to High Thermoelectric Performance.

Orthorhombic GeSe is a promising thermoelectric material. However, large band gap and strong covalent bonding result in a low thermoelectric figure of merit, zT≈0.2. Here, we demonstrate a maximum zT≈1.35 at 627 K in p-type polycrystalline rhombohedral (GeSe)0.9 (AgBiTe2 )0.1 , which is the highest value reported among GeSe based materials. The rhombohedral phase is stable in ambient conditions for x=0.8-0.29 in (GeSe)1-x (AgBiTe2 )x . The structural transformation accompanies change from covalent bonding in orthorhombic GeSe to metavalent bonding in rhombohedral (GeSe)1-x (AgBiTe2 )x . (GeSe)0.9 (AgBiTe2 )0.1 has closely lying primary and secondary valence bands (within 0.25-0.30 eV), which results in high power factor 12.8 μW cm-1 K-2 at 627 K. It also exhibits intrinsically low lattice thermal conductivity (0.38 Wm-1 K-1 at 578 K). Theoretical phonon dispersion calculations reveal vicinity of a ferroelectric instability, with large anomalous Born effective charges and high optical dielectric constant, which, in concurrence with high effective coordination number, low band gap and moderate electrical conductivity, corroborate metavalent bonding in (GeSe)0.9 (AgBiTe2 )0.1 . We confirmed the presence of low energy phonon modes and local ferroelectric domains using heat capacity measurement (3-30 K) and switching spectroscopy in piezoresponse force microscopy, respectively.

Metavalent Bonding in GeSe Leads to High Thermoelectric Performance

AbstractOrthorhombic GeSe is a promising thermoelectric material. However, large band gap and strong covalent bonding result in a low thermoelectric figure of merit, zT≈0.2. Here, we demonstrate a maximum zT≈1.35 at 627 K in p‐type polycrystalline rhombohedral (GeSe)0.9(AgBiTe2)0.1 , which is the highest value reported among GeSe based materials. The rhombohedral phase is stable in ambient conditions for x=0.8–0.29 in (GeSe)1−x(AgBiTe2)x . The structural transformation accompanies change from covalent bonding in orthorhombic GeSe to metavalent bonding in rhombohedral (GeSe)1−x(AgBiTe2)x . (GeSe)0.9(AgBiTe2)0.1 has closely lying primary and secondary valence bands (within 0.25–0.30 eV), which results in high power factor 12.8 μW cm−1 K−2 at 627 K. It also exhibits intrinsically low lattice thermal conductivity (0.38 Wm−1 K−1 at 578 K). Theoretical phonon dispersion calculations reveal vicinity of a ferroelectric instability, with large anomalous Born effective charges and high optical dielectric constant, which, in concurrence with high effective coordination number, low band gap and moderate electrical conductivity, corroborate metavalent bonding in (GeSe)0.9(AgBiTe2)0.1. We confirmed the presence of low energy phonon modes and local ferroelectric domains using heat capacity measurement (3–30 K) and switching spectroscopy in piezoresponse force microscopy, respectively.

Single Atomic Cerium Sites with a High Coordination Number for Efficient Oxygen Reduction in Proton-Exchange Membrane Fuel Cells

Fe–N–C electrocatalysts, as a representative of platinum group metal-free (PGM-free) catalysts, exhibit a comparable oxygen reduction reaction (ORR) activity but insufficient stability to that of commercial Pt/C in proton-exchange membrane fuel cells (PEMFCs), due to the unavoidable Fenton’s reactions. Herein, we report a hard-template approach to synthesize the rare-earth single-cerium-atom-doped metal–organic frameworks with a hierarchically macro–meso–microporous structure. Spherical aberration correction electron microscopy confirms the atomic dispersion of Ce sites. Additionally, X-ray absorption spectroscopy (XAS) was employed to further verify the coordination environment of Ce sites, which were stabilized by four-coordinated nitrogen atoms and six-oxygen atoms (Ce–N4/O6). The Ce sites were embedded in a hierarchically macro–meso–microporous N-doped carbon (Ce SAS/HPNC) catalyst, which exhibits a half-wave potential of 0.862 V in ORR and the highest power density of 0.525 W cm–2 under 2.0 bar H2/O2 in the fuel cell test.

Polymorphs of the Gadolinite-Type Borates ZrB2 O5 and HfB2 O5 Under Extreme Pressure.

Based on the results from previous high‐pressure experiments on the gadolinite‐type mineral datolite, CaBSiO4(OH), the behavior of the isostructural borates β‐HfB2O5 and β‐ZrB2O5 have been studied by synchrotron‐based in situ high‐pressure single‐crystal X‐ray diffraction experiments. On compression to 120 GPa, both borate layer‐structures are preserved. Additionally, at ≈114 GPa, the formation of a second phase can be observed in both compounds. The new high‐pressure modification γ‐ZrB2O5 features a rearrangement of the corner‐sharing BO4 tetrahedra, while still maintaining the four‐ and eight‐membered rings. The new phase γ‐HfB2O5 contains ten‐membered rings including the rare structural motif of edge‐sharing BO4 tetrahedra with exceptionally short B−O and B⋅⋅⋅B distances. For both structures, unusually high coordination numbers are found for the transition metal cations, with ninefold coordinated Hf4+, and tenfold coordinated Zr4+, respectively. These findings remarkably show the potential of cold compression as a low‐energy pathway to discover metastable structures that exhibit new coordinations and structural motifs.

Influences of pH and EDTA Additive on the Structure of Ni Films Electrodeposited by Using Bubble Templates as Electrocatalysts for Hydrogen Evolution Reaction

The structure of Ni films is essential to their electrocatalytic performance for hydrogen evolution reaction (HER). The pH value and EDTA (ethylene diamine tetraacetic acid) additive are important factors for the structure control of electrodeposited metal films due to their adjustment of metal electrocrystallization and hydrogen evolution side reactions. The structures of Ni films from 3D (three-dimensional) porous to compact and flat structure are electrodeposited by adjusting solution pH values or adding EDTA. It is found that when pH value increases from 7.7 to 8.1, 3D porous films change to compact films with many protrusions. Further increasing the pH value or adding 0.1 M EDTA causes compact and flat films without protrusions to appear. When pH ≤ 7.7, hydrogen bubbles with large break-off diameter are easily adsorbed on film surface acting as porous structure templates, and the electroactive ion species, Ni2+ and Ni(NH3)n2+ complexes with low coordination number (n ≤ 3), possess high reduction overpotential, which is beneficial to forming protrusions and smaller particles. So, porous Ni films are electrodeposited. In solutions with pH ≥ 8.1 or 0.1 M EDTA, Ni(NH3)n2+ complexes with high coordination number (6 ≥ n ≥ 3) and hexadentate chelate are formed. Due to the improved wettability, bubbles with a small break-off diameter rapidly detach the film surface resulting in strong stirring. The reduction overpotential is reduced, leading to the formation of larger particles. Therefore, the solution leveling ability increases, and it is difficult to form protrusions, thus it forms a compact and flat film. The 3D porous film exhibits excellent catalytic performance for HER due to the large catalytic activity area.

Describing Polytopal Rearrangement Processes of Octacoordinate Structures. I. Renewed Insights into Fluxionality of the Rhenium Polyhydride Complex ReH5(PPh3)2(Pyridine)

Hydride ligands of transition metal polyhydride complexes with a high coordination number are prone to fluxionality leading to interesting structural dynamics. However, the underlying polytopal rearrangement pathways have been rarely studied. Based on quantum chemical calculations carried out in this work with density functional theory and coupled-cluster theory, two new fluxional mechanisms have been identified for the rhenium polyhydride complex ReH5(PPh3)2(pyridine) to jointly account for two consecutive coalescence events in the variable-temperature NMR spectra upon heating: lateral and basal three-arm turnstile rotation. The frequently cited pseudorotation in ReH5(PPh3)2(pyridine) (Lee et al. Inorg. Chem. 1996, 35, 695) turns out to be a three-step process including two lateral three-arm turnstile steps and one basal turnstile step in between. The new fluxional mechanisms discovered in this work may also exist in other transition metal polyhydrides.

Variation in Properties of Pre-Nucleation Calcium Carbonate Clusters Induced by Aggregation: A Molecular Dynamics Study

Numerous studies have speculated calcium carbonate (CaCO3) nucleation induced by pre-nucleation clusters (PNCs) aggregation. However, it is challenging for experiments to directly obtain the relationship between PNCs aggregation and nucleation. Herein, we employ molecular dynamics simulations to explore the variation during PNCs aggregation, which can describe the beginning stage of CaCO3 nucleation induced by PNCs aggregation in supersaturated solutions. The results reveal that the formation of CaCO3 nucleus consists of PNCs spontaneous growth, PNCs solubility equilibrium, and aggregation of PNCs inducing nucleation. The PNCs aggregation, accompanied by the variation in the configuration and stability of CaCO3 aggregate, breaks the solubility equilibrium of PNCs and creates conditions for the formation of the more stable nucleus. Besides, the CaCO3 nucleus with the higher coordination number and the lower hydration number form when decreasing the CaCO3 concentration or increasing the temperature. This work not only sheds light on the formation of the CaCO3 nucleus but also contributes to the explanation for CaCO3 polymorphism.

Transforming cobalt hydroxide nanowires into single atom site catalysts

Abstract The stability of the catalyst has always received considerable attention in materials science and catalysis. Single atom site catalysts (SACs) with high surface energy and low coordination number are generally believed not as stable as nanocatalysts. Herein, we discovered that nanocrystals, such as nanowires (NWs), which are unstable at high temperature, can be directly converted into SACs without undergoing particles aggregation and growth. In-situ environmental transmission electron microscopy, X-ray absorption spectroscopy, and density functional calculation studies demonstrated that the high temperature overcomes the energy barrier of metal atomization while N-doped carbon materials regulate the atomic adsorption energy, both of which jointly cause the transformation of NWs into SACs. Notably, the obtained SACs exhibited excellent catalytic performance for the hydrogenation of nitroarenes to the corresponding amines due to the considerable decrease in energy barriers of the rate-determining step.

Multi‐Center Hyperbonding in Phase‐Change Materials

A comprehensive understanding of chemical interactions underlying the network structure of chalcogenide materials is a crucial prerequisite for comprehending their microscopic structures, physicochemical properties, and capabilities for current or potential applications. However, for many chalcogenide materials, an inherent difficulty is often present in investigating their chemical properties, due to the involvement of delocalized bonding and non‐bonding (“lone‐pair”) electrons, which requires interaction mechanisms beyond that of conventional two‐center, two‐electron covalent bonding. Herein, some recent progress in the development of new interatomic interaction models for chalcogenides is reviewed, in particular focusing on the multi‐center hyperbonding model, proposed in an effort to resolve this issue. The capability of this model in elucidating a diversity of interesting material properties of phase‐change materials (PCMs) is highlighted, including Ge2Sb2Te5 (GST). These include the propensity of high coordination numbers of constituent atoms, linear triatomic bonding geometries with short and long bonds (often ascribed to the effect of a Peierls distortion), abnormally large Born effective charges of crystalline GST, large optical contrast between amorphous and crystalline GST, ultrafast crystallization speed of amorphous GST, and the chemical origin differentiating non‐PCM from PCM chalcogenide materials. Other bonding models for these materials are also briefly discussed.