Electronegativity Scale Research Articles

Ultrafast synthesis and luminescence properties of rare earth orthoniobates RENbO4 (RE = La, Eu, Gd, Yb, Lu)

Rare earth orthoniobates (RENbO4) are one kind of important functional materials due to its applications in solid-state phosphors, thermal barrier coatings, and microwave dielectric ceramics. The synthesis of rare earth niobates often needs high reaction temperatures (1300 °C–1700 °C) and long processing times (from hours to tens of hours) in solid-state reactions, which can increase the study time of the relationship between structure and properties. In this work, we used ultrafast high-temperature sintering method to synthesize RENbO4 (RE = La, Eu, Gd, Yb, Lu), and found specific structure and properties in these materials obtained with specific synthetic techniques. Based on the electronegativity scale, the charge transfer energy of lanthanide ions in the YNbO4 crystal was calculated. The rapid synthesis of RENbO4 in a vacuum atmosphere generated more oxygen vacancies, and the structures of [REO8] and [NbO6] were distorted. The shortening of the fluorescence lifetime of LaNbO4 and EuNbO4 was related to the formation of self-trapped excitons facilitated by lattice distortion. The emission peak of LuNbO4 at about 530 nm is attributed to the oxygen vacancy in the niobate group. The reported synthetic methods can provide a fast materials screening route for high melting point inorganic materials.

High-throughput assessment of stability and mechanical properties of medium- and high-entropy carbides: Bridging empirical criteria and ab-initio calculations

This study assesses the effectiveness of empirical stability descriptors — the normalized geometric packing parameter, lattice size difference, electronegativities mismatch, and the convex hull analysis based on information on mutually dissolving components, and ab-initio calculated entropy forming ability (EFA) for high-throughput materials discovery in high-entropy ceramics. A sample containing 53,130 medium and high-entropy carbide combinations from the Materials Project database has been analyzed, comparing solid solutions selected based on empirical descriptors and EFA calculations. The suitability of various electronegativity scales is evaluated, while Automatic FLOW (AFLOW) partial occupation (AFLOW-POCC) and special quasirandom structures (SQS) calculations provide insights into enthalpies, bulk moduli, and lattice parameters. It is shown that local distortions play a role in determining the stability of high-entropy ceramics and estimated lattice parameters, Young’s modulus, fracture toughness, and Vickers hardness by computational and experimental approaches. Our analysis demonstrates the efficacy of density functional theory (DFT) approaches for high-throughput screening and highlights the need for the further exploration of the cocktail effect on high-entropy ceramics’ mechanical properties.

Density functional model of threshold voltage shifts at High-K/Metal gates

A density functional analysis of oxide dipole layers used to set the threshold voltages in high-K/metal CMOS gate stacks is given in terms of the band alignments and chemical trends of these component oxide layers. The oxides SrO, La2O3, HfO2 and Al2O3 are found to have similar band gaps and form a ‘staircase’ of band alignments, allowing them to shift the metal electrode Fermi level in both n-type and p-type directions. This analysis supersedes previous largely empirical models based on metal oxide ion densities or electronegativity scales.

Quantitative applications of the electronegativity scale

Quantitative applications of the electronegativity scale

Machine-learning-assisted modeling of alloy ordering phenomena at the electronic scale through electronegativity

Many studies attribute the excellent properties of high-entropy alloys to the ordering-phenomena. It can be known from density functional theory that the macroscopic properties of the system can be described by the electron density. Electronegativity is related to electron density, and models describing ordering can be established based on electronegativity scales through machine learning. In this study, a large dataset was established and predicted the ordered state corresponding to the alloy composition. The accuracy of the model on the test set was 94%. Furthermore, this study used different methods to explain the machine learning model and learned more model information.

Universal scales of electronegativity and ionicity from electron scattering factors.

Electronegativity and ionicity are important but difficult concepts. In this work, we present the universal scale of electronegativity by utilizing electron scattering factors. A mapping of our proposed "scattering electronegativity" with Pauling electronegativity and other electronegativity scales is given. Two new ionicity scales based on electron scattering factors are also proposed and compared with Philips's ionicity and Pauling's ionicity. Although electron scattering factors are based on neutral, free, atomic features, scattering electronegativity and ionicity are able to provide rich charge or bonding information of materials in molecules or solid states. Our newly proposed electronegativity scale satisfies the metalloid band criterion (or Si rule). A new Mg rule and a new concept of critical ionicity gap are proposed, successfully distinguishing between the four-fold and six-fold coordinates in the ANB8-N crystals.

Density functional analysis of oxide dipole layer voltage shifts in high κ/metal gate stacks

The mechanism of gate threshold voltage (VT) shifts observed in high κ/metal gate stacks is investigated by a density functional theory. This finds that VT depends on the band alignments and the chemical trends between the component oxide layers, such as HfO2, SrO, La2O3, Al2O3, and SiO2. Based on the electron counting rule, we have built three insulating SiO2/SrO, SiO2/La2O3, and SiO2/Al2O3 interfaces, all of which feature a clean bandgap. Two methods have been adopted to derive the band alignments between these four oxides, which are consistent with each other. The results show staggered, “staircase” band alignments and enable La2O3 and Al2O3 layers to shift the metal electrode Fermi level in opposite directions and to approach the Si conduction band and valence band edge positions, respectively. This analysis updates previous empirical models of this effect based on metal oxide ion densities or electronegativity scales and confirms that the oxide layer scheme is suitable for controlling the effective metal work functions in metal–oxide–semiconductor field-effect transistors.

Electronic Properties of Functionalized Diamanes for Field-Emission Displays.

Ultrathin diamond films, or diamanes, are promising quasi-2D materials that are characterized by high stiffness, extreme wear resistance, high thermal conductivity, and chemical stability. Surface functionalization of multilayer graphene with different stackings of layers could be an interesting opportunity to induce proper electronic properties into diamanes. Combination of these electronic properties together with extraordinary mechanical ones will lead to their applications as field-emission displays substituting original devices with light-emitting diodes or organic light-emitting diodes. In the present study, we focus on the electronic properties of fluorinated and hydrogenated diamanes with (111), (110), (0001), (101̅0), and (2̅110) crystallographic orientations of surfaces of various thicknesses by using first-principles calculations and Bader analysis of electron density. We see that fluorine induces an occupied surface electronic state, while hydrogen modifies the occupied bulk state and also induces unoccupied surface states. Furthermore, a lower number of layers is necessary for hydrogenated diamanes to achieve the convergence of the work function in comparison with fluorinated diamanes, with the exception of fluorinated (110) and (2̅110) films that achieve rapid convergence and have the same behavior as other hydrogenated surfaces. This induces a modification of the work function with an increase of the number of layers that makes hydrogenated (2̅110) diamanes the most suitable surface for field-emission displays, better than the fluorinated counterparts. In addition, a quasi-quantitative descriptor of surface dipole moment based on the Tantardini-Oganov electronegativity scale is introduced as the average of bond dipole moments between the surface atoms. This new fundamental descriptor is capable of predicting a priori the bond dipole moment and may be considered as a new useful feature for crystal structure prediction based on artificial intelligence.

A network-based correlation research between element electronegativity and node importance

Abstract Abstracted from real compounds, chemical elements can be considered a system tied by chemical bonds (or bonding relationships) between two elements, namely the chemical element and chemical bond system. Then, elements, bonds and their properties can be studied from the view of complex networks. Based on the previous work, we introduce bond polarity to judge edge direction and select four electronegativity scales to build the directed chemical bond networks. Taking node importance and element electronegativity as an example, we discuss the relationships of properties between chemistry and networks. Through quantitative analysis, the importance scale changing trends in all networks are found to follow the similar periodic laws. And there exist statistically significant correlations between most of scale pairs. The further analysis proves the similar chemical meanings between above two scales. All these conclusions are unassociated with specific electronegativity scales, even if their networks have different nodes and edges, which prove the rationality and universality of the proposed method. Our research gives a network explanation on element electronegativity, and we can study more objects and chemical properties from the view of complex networks.

An FSGO based Electronegativity Scale invoking the Electrophilicity Index

AbstractElectronegativity is an important chemical construct that plays a pivotal role to explain several chemical, biochemical and physicochemical phenomena. The study of this periodic descriptor is still considered an active domain of research, and a number of scientists are involved to propose different scales of electronegativity based on experimental findings and theoretical concepts. In this study, we have proposed a model to compute atomic electronegativity values of 103 elements based on the Floating Spherical Gaussian Orbital approach invoking the atomic electrophilicity index as a descriptor. The computed electronegativity scale observes the periodic trend and justifies many chemical phenomena. Molecular electronegativity values have also been computed using the computed atomic electronegativity data and utilized to justify the Electronegativity Equalization Principle. In order to validate our proposed model, internuclear bond distances for some molecules have been deduced in terms of our computed atomic electronegativity data. A strong correlation with experimental counterparts proves the efficacy of our proposed model.

Understanding of the bond covalency nature with ionic electronegativity in perovskite cuprates La2CuMO6-x (M = Ti, Mn, Ru)

A bond valence sums (BVS) modified ionic electronegativity (EN) scale was suggested for better accommodating the double perovskite La2CuMO6-x (M ​= ​Ti, Mn, Ru) with mixed bonding nature. Both the M ​− ​O bond covalency fraction (f) and the cooperative B-site sublattice distortion are highlighted to connect structure and physical properties. Particularly, the Ti-based compound hosts the largest M/O ionic EN difference and hence yields the smallest f value while the Ru-based analogue exhibits the opposite result. As the consequence, robust spin disordering accompany with poor dc conductivity is convinced in the Ti-based sample owing to its featuring B-site ionic arrangement and profound suppression of 3d(Ti)-2p(O) orbital hybridization. For the Ru-based sample, strong ferromagnetic spin frustration and low charge carrier hopping potential might be essentially ascribed to its large f value through enhancing orbital degeneracy between 4d(eg)-2p σ and 4d(t2g)-2p π bonding states. The Mn-based sample with the moderate f value exhibits the similar magnetic and electric behaviors as those of Ru-based sample. Both the d(M)-p(O) orbital hybridization and the M ​− ​O bond covalency could be tuned by rationally selecting the M cation with proper ionic EN value. This work provides a deep understanding of the bond covalency nature in perovskite cuprates and might help to develop novel electronic functional materials.

A Scale of Atomic Electronegativity Based on Floating Spherical Gaussian Orbital Approach

AbstractElectronegativity (χ) is an old yet valuable concept having multidisciplinary applications. To advance the understanding of this concept, an electronegativity model has been proposed based on polarizability within the context of Floating Spherical Gaussian Orbital (FSGO) approach. The model provides atomic electronegativity scale for 120 elements. The calculated electronegativity presents marked periodicity and relates well with other electronegativity scales. Further, Electronegativity Equalization Principle is validated by the computed electronegativity data. The proposed scale has also been successfully applied to compute Fermi energy for some metal oxides. In accordance with the literature, this is the first FSGO‐polarizability based model of electronegativity.

The Correlation between the Electronegativities and the Standard Potentials

Electronegativity [1.2] can be defined as the ability of an atom in molecule to draw covalent bonding electrons to itself from the intermediate state in which electrons are equally bound with each atom. The equal bonds of electrons with atoms would be compensated in the intermediate state. However, there should be saved the definite simple non-specific electrostatic (coulomb) attraction of bonding electrons with each polarized atom in this intermediate state [3-5]. Such a non-specific intermediate bond of electrons is revealed between thermodynamic non-stable specific bonds of electrons in reductant and thermodynamic stable specific bonds of electrons in oxidants. Due to this reductants are able spontaneously give up electrons in chemical interactions. Oxidants can only accept electrons in chemical interactions if their own electrons are bound thermodynamically stable [3]. The intermediate electron bond is revealed in the correlations [6-10] between the standard potentials E o and electronegativities χa of metal and non-metal electrodes (Fig.1.2) and between the standard potential E o and the electron work functions W e of metals (Fig.3) [1,2].The charges of potential-dependable ions are shown in Fig.1-3. In the coordinates χa - E o, with the increase of the empirical electronegativies χa the reducing activity of typical metals (in the line Na --- Te) decrease and then the oxidation activity of halogens increase (in the line I ---- F). On the other side, with increase of χa the oxidation activity of cations-oxidants decrease (in the line Au+ --- Te4+) and then the reducing activity of anions-reductant (S2-, Se2-) increase. These relations are intersected at the standard potential ~ +0.5 V SHE and the intermediate χa,interm ~ 2 that is between electronegativities for metals (tellurium Te) and non-metals (iodine I), Fig.1. In the coordinates χ - E o, two average lines are also intersected at ~ +0.5 V SHE (Fig.2). At that, the deviations appear for halogens and transition metals in the cordinates χ - E o. There is the maximum of the correlation between the electron work functions of metals W e and the standard potentials E o of metal electrodes. This maximum is characterized by the same standard potential ~ + 0.5 V SHE and the electron work functions W e = ~ 5.2 eV between the known W e = ~ 5.0 eV for tellurium and W e = ~ 5.4 eV for iodine. This electron work function W e = ~ 5.2 eV is the highest one for typical metals (reductants) and the least one for non-metals (oxidants). It is concluded that the intermediate electronegativity (Fig.1-3) and the standard potential ~ +0.5 V SHE should characterize some electrode form (neither metal nor non-metals with the intermediate bond of outer electrons). The intermediate electron bond is not enough unstable for spontaneous giving electrons and not enough stable to accept electrons by such a hypothetical form. Such a form would not be able to reduce or oxidize itself water molecules, i.e., the electrode interaction would be absent. The chemical equilibrium of half-reactions in the center of the electrochemical series (Fig.1-3) is thermodynamically equal to the absence of the electrode interaction. The standard potential ~ +0.5 V SHE is close to Billiter potential +0.475 V SHE [3, 8]. It was determined that the intermediate electron state between thermodynamic stable and unstable electron states is characterized more exactly by the ionization energy ~5.18 ÷ 5.19 eV. [3,10]. The explanations of the correlation in the coordinatesw χ - E o are given. The changes of the electronegativity χa - χa,interm define the formation and accepting of intermediate non-specific bound electrons in half-reactions - halves of summary oxidation-reduction reactions and changes of free energies in them [4,5].References(1) L. Pauling, The Nature of the Chemical Bonds, Cornell University Press, Ithaca,1960.(2) A.l Allred, E.G. Rochow, A scale of electronegativity based on electrostatic force, J. Inorg Nucl.Chem. 1958, 5,264-268.(3) A.I.Chernomorskii, The Intermediate Energy Level of Electrons, Dokl. Akad. Nauk Uzb.SSR. 1979, 6, 25-26.(4) A.I.Chernomorskii, Calculation of the Free Energie of Electrode Reactions, Zh.Fiz.Khim. 1978, 53, 757-759.(5) A.I.Chernomorskii, The Nature of Individual Electrode Reactions, Zh.Fiz.Khim. 1981, 55, 474-475. (6) A.I.Chernomorskii, Analysis of the Relations between Electrochemical Characteristics of Metals, the Electronegativities and Electron Work Functions, Dokl. Akad. Nauk Uzb.SSR. 1988,2, 36-39.(7) A.I.Chernomorskii, Relations between Physical Chemical Characteristics and the Standard Potentials of Metals, Dokl. Akad. Nauk Uzb.SSR. 1982,12, 25- 27.(8) A.I.Chernomorskii, Thermodynamics of the Reversible Electrodes, FAN, Tashkent,1982.(9) A.I.Chernomorskii, Thermodynamics of Electrodes, FAN, Tashkent,1993.(10) A.I.Chernomorskii, The Intermediate Electron Bond and Half-Reactions, Scientific Resources, New York, 1999. Figure 1

On the Predictive Power of Chemical Concepts.

Many chemical concepts can be well defined in the context of quantum chemical theories. Examples are the electronegativity scale of Mulliken and Jaffé and the hard and soft acids and bases concept of Pearson. The sound theoretical basis allows for a systematic definition of such concepts. However, while they are often used to describe and compare chemical processes in terms of reactivity, their predictive power remains unclear. In this work, we elaborate on the predictive potential of chemical reactivity concepts, which can be crucial for autonomous reaction exploration protocols to guide them by first-principles heuristics that exploit these concepts.

Thermochemical electronegativities of the elements

Electronegativity is a key property of the elements. Being useful in rationalizing stability, structure and properties of molecules and solids, it has shaped much of the thinking in the fields of structural chemistry and solid state chemistry and physics. There are many definitions of electronegativity, which can be roughly classified as either spectroscopic (these are defined for isolated atoms) or thermochemical (characterizing bond energies and heats of formation of compounds). The most widely used is the thermochemical Pauling’s scale, where electronegativities have units of eV1/2. Here we identify drawbacks in the definition of Pauling’s electronegativity scale—and, correcting them, arrive at our thermochemical scale, where electronegativities are dimensionless numbers. Our scale displays intuitively correct trends for the 118 elements and leads to an improved description of chemical bonding (e.g., bond polarity) and thermochemistry.

An alternative indicator of annihilated electrons in atoms: Rahm's electronegativity scale

In this study, we calculated the theoretical gamma-ray spectra of the first 36 representative elements in groups 1, 2, and 13-18. We found that the width of these atoms' gamma-ray spectra is proportional to the value of the corresponding Rahm's electronegativity (Eg). Based on this, we present a new explanation of the width of the gamma-ray spectra. We also define a new physical quantity, average Doppler shift (ADS). ADS can quantitatively verify that positrophilic electrons in the positron-electron annihilation process are valence electrons. ADS also can express some characteristics of the gamma-ray spectra such as the full width at half maximum (FWHM), and even more general than FWHM in some cases. Both the FWHM and ADS of the gamma-ray spectra in light elements agree with the corresponding Rahm's electronegativity values, respectively. ADS provides strong evidence in favour of Rahm's electronegativity scale. It is expected that this will be useful for understanding the mechanism of the positron-electron annihilation process.

METAVALENT CHEMICAL COMPOUNDS OF THE TYPE AIBVCVI2 (AI – Li, Na, K, Rb, Cs; BV – As, Sb, Bi; CVI – Se, Te)

The concept of chemical bonding is one of the key concepts in the modern chemical science. The main types of chemical bonds traditionally distinguished in the scientific literature are ionic, covalent and metallic; whereas hydrogen bonds and intermolecular interaction forces are usually taken as secondary bonds. It should be noted, however, that there are no sharp boundaries for the above types of chemical bonds.In order to predict the type of chemical bond between atomic particles, a special atomic property called the electronegativity [i.e. the ability of a given atom in a molecule to attract electron density (or valent electrons)] is widely used. The concept of electronegativity and the first scale of electronegativities of chemical elements were proposed by L. Pauling in 1932; later, several alternative scales of electronegativities were developed, including those by Mulliken and by Allred–Rochow.Using the difference between the electronegativities of atoms (DEN) and the sum of the electronegativities of atoms (SEN), one can obtain quantitative parameters which characterize the chemical bonds in specific compounds. In particular, the difference in the electronegativities of the A and B atoms characterizes the degree of ionicity for the A–B bond, while the sum of electronegativities indicates either the degree of covalency (at relatively large SEN values) or the degree of metallicity (at low SEN values). The sum of electronegativities can be replaced, if necessary, by the average electronegativity (ENav.) of the compound. Taking the elementary substances Cs and F2 and the binary compound CsF as reference points in the coordinates ENav.–DEN, a diagram triangle was constructed, which conveniently and clearly illustrates the type of chemical bond of different chemical compounds.The analysis of the ternary chalcogenide AIBVCVI2 (AI – Li, Na, K, Rb, Cs; BV – As, Sb, Bi; CVI – Se, Te) compounds (which have been studied for a long time by the researchers of the Uzhhorod National University) by using the aforementioned diagram triangle in the coordinates ENav.–DEN has revealed the fact that the considered compounds are characterized by the combined (so-called "metavalent") chemical bonding recently identified in the specialized scientific literature as a separate bonding type.

Averaged Scale in Electronegativity Joined to Physicochemical Perturbations. Consequences of Periodicity.

In this work, we propose a new representative electronegativity scale χDC based on a statistical analysis of 11 electronegativity scales associated with electric ionic resonance energy, ionization potential, electron affinity, polarizability, electric force, average orbital energy, chemical potential, electrochemical reduction potential, and electric potential energy. Among these scales, it is the new PE° electronegativity scale, which relates the reduction potential E° to Pauling’s electronegativity scale. The scale χDC gives more weight to the physicochemical factors, which influence the electronegativity, but this scale is not necessarily the best electronegativity scale for the element. This scale is based on (1) the average of the experimental electronegativity values; (2) the proximity of an experimental value to the average given by the difference and the ratio to this average; (3) in critical cases, the periodicity network of the periods and the groups; and (4) the periodicity of the sequence of the ratios of the experimental electronegativity values to the best-selected electronegativity value. We have also taken as probe scales Nagle’s, Allred and Rochow’s, Allen’s (Hoffman’s and Politzer’s), PE°, Gordy’s, and Ghosh’s electronegativity scales in order to investigate the trend of the physicochemical factors which influence the electronegativity. With this trend, we have determined zones where a physicochemical property influences the electronegativity more. We have also found that physicochemical perturbations such as the orbital overlap, the stable configurations, the nephelauxetic effect, the width of the band gap, the ligand field stabilization energy, the penetration of the orbitals, and the lattice energy influence the electronegativity. Besides, we have analyzed the exactness of the electronegativity of the scales through the periodical ranking, the chemical tripartite separation among ionic, covalent, or metallic bond (taking into account the amplitude of the metalloid band), and the physicochemical property of bond force. The representative χDC electronegativity scale is the best in periodicity, followed by Batsanov’s and Pauling’s scales. In the type of chemical bond, the ranking depends on the number and kind of compounds in the sample, but in general, Pauling’s, the ARS, and Batsanov’s electronegativity scales are the best with a confidence interval of 95%. On the other hand, in the physical bond force, Batsanov’s, Pauling’s, Mulliken’s, Nagle’s, Allen’s, the ARS, and the χDC electronegativity scales are the best scales. Also, we have considered the free atom and the in situ hypotheses of electronegativity and used the low and high oxidation states to verify these hypotheses. Besides, as an example of the utility of this ranking of scales, we have analyzed the relation of lanthanum La and lutetium Lu to Group 3, lanthanides, and hafnium Hf. We also analyze the vertical, horizontal, Knight’s move, and isodiagonal periodicity of the electronegativity and associate this periodicity to a similar chemical–physical behavior of elements or ions.

Coupled cluster study of the partial charge of hydrogen in HnX molecules in s and p block: Relationship with electronegativity

Bader analysis of HnX was performed using densities generated by second-order one electron Douglas-Kroll-Hess (DKH) Hamiltonian RCCSD(T)//aug-cc-pVTZ level of theory for the 2p, 3p and 4p subshells, and by DKH Hamiltonian RCCSD(T)//aug-cc-pVTZ-PP for the 5p and 6p subshells. The partial charges of hydrogen atoms are closely related to the original definition of electronegativity. Direct computational results of hydrogen partial charges were tabulated in a table and compared to the Pauling electronegativity scale as well as other electronegativity scales. A strong correlation between these different scales and the computational results for hydrogen partial charges was found.

A new approach to compute atomic electrophilicity index in terms of Gordy’s electronegativity

Electrophilicity index is a well-known Conceptual Density Functional Theory–based reactivity descriptor to explain a wide range of physicochemical behaviours. In the present work, an attempt is made to evaluate a new electrophilicity index scale in terms of nucleophilicity index relying on Gordy’s electronegativity scale. The computation is performed for 103 elements of the periodic table invoking regression analysis. The new set of electrophilicity index satisfies the sine qua non of a standard scale. Electrophilicity Equalization Principle is also validated by our computed data. It is put forward that the new scale will be useful in understanding various physicochemical properties and related phenomenon.