Bond Theory Research Articles

The relationship between activated H2 bond length and adsorption distance on MXenes identified with graph neural network and resonating valence bond theory

Motivated by the recent experimental study on hydrogen storage in MXene multilayers [Liu et al., Nat. Nanotechnol. 16, 331 (2021)], for the first time we propose a workflow to computationally screen 23 857 compounds of MXene to explore the general relation between the activated H2 bond length and adsorption distance. By using density functional theory we generate a dataset to investigate the adsorption geometries of hydrogen on MXenes, based on which we train physics-informed atomistic line graph neural networks (ALIGNNs) to predict adsorption parameters. To fit the results, we further derived a formula that quantitatively reproduces the dependence of H2 bond length on the adsorption distance from MXenes within the framework of Pauling's resonating valence bond theory, revealing the impact of transition metal’s ligancy and valence on activating dihydrogen in H2 storage.

Novel red phosphor Ba0.3Sr0.7SiO3:Eu3+ with excellent quantum yield and thermal stability

Developing high-performance red phosphors remains an urgent issue in the field of green lighting. In this work, a novel red phosphors Ba0.3Sr0.7-xSiO3:xEu3+(0.02 ≤ x ≤ 0.12, Δx=0.02) were successfully synthesized by high-temperature solid-state reaction, and systematically studied theirs crystal structure, microstructure, fluorescence spectrum, thermal stability, fluorescence lifetime, and chromaticity coordinates. The phosphors are all monoclinic crystal system, and space group is C12/c1. It is inferred from the chemical bond theory that Eu3+ occupies the site of Sr2+ in the matrix. The emission spectrum of Ba0.3Sr0.64SiO3:0.06Eu3+ exhibits strong 5D0→7F4 (702nm) emission, which made its color purity as high as 97.1756 %. Additionally, The quantum yield of Ba0.3Sr0.64SiO3:0.06Eu3+ phosphor is as high as 88.60 %, and it exhibits excellent thermal stability with the thermal activation energy Ea = 0.3893 eV. Therefore, Ba0.3Sr0.7SiO3:Eu3+ phosphors can be an ideal candidate material for white LED.

Research status of phase change memory and its materials

Phase change memory technology is a new technology in non-volatile memory technology. Phase change memory technology has many advantages, such as non-volatility, high reading and writing speeds, better data retention, and strong compatibility with CMOS technology, and has been paid attention to by many researchers. Phase change materials are mainly chalcogenide compound materials. Researchers have done a lot of research on Ge-Sb-Te, Ge-Te, and Sb-Te-based phase change materials and developed some new phase change material systems. In addition, researchers have carried out in-depth research on the phase transition mechanism, but the existing atomic umbrella jump theory, multiple ring theory, resonance bond theory, octahedral structure theory, etc. have not formed a unified understanding of the phase transition mechanism. At present, phase change memory is mainly prepared by magnetron sputtering of phase change material targets, which results in fast deposition and high purity of the prepared film. In this paper, based on the development of phase change storage materials, the system of phase change materials and its phase change mechanism, the phase transition mechanism of phase change memory, the preparation and characterization methods of phase change films, the industrialization progress, and other research work are reviewed.

Crystal structure, chemical bonding and infrared reflectivity of microwave dielectric SrIn2O4 ceramics

In this work, the orthorhombic structured SrIn2O4 ceramics with a space group Pnam were synthesized by a solid-state reaction method. A high relative density (96.5%) coupled with excellent microwave dielectric properties (εr ~ 12.3, Q × f = 96,900 GHz, τf ~ -61.6 ppm/°C) were obtained as sintered 1300 °C for 4 h. The bond valence analysis demonstrates that the large sized cation Sr2+ exhibits a compressed state, while the In3+ exhibits a weaken rattling effect. The P-V-L chemical bond theory analysis indicates that the In-O bonds play a key role in affecting the dielectric loss. The thermally conductivity activation energy Edc (0.94 eV) of SrIn2O4 was obtained by the dielectric spectroscopy, indicating that the Edc was contributed to the double ionized oxygen vacancies. Furthermore, the intrinsic dielectric properties (εr ~ 11.2, Q × f = 148,900 GHz) of SrIn2O4 were obtained by infrared reflectivity spectroscopy.

Microwave dielectric properties and sintering behavior of a novel low-cost lightweight,middle-εr Na2Ti6O13 ceramics

In order to develop novel lightweight low-cost microwave dielectric ceramics (MDCs), middle-εr Na2Ti6O13 ceramics were prepared by a traditional solid-state reaction method and the sintering behavior and microwave dielectric properties ((MDPs) were investigated. The detailed structural parameters of the Na2Ti6O13 ceramics were obtained by X-ray diffraction and Rietveld refinement, and the chemical bond characteristics of the structures were further studied using Raman spectroscopy. The relative density of the ceramics and scanning electron microscopy (SEM) images show that density and porosity are important factors affecting the dielectric properties of the samples. Based on the acquired Raman spectra and complex chemical bond theory (P–V–L theory), the chemical bond properties were calculated and analyzed, and the effects of intrinsic factors on the MDPs were investigated. The MDPs of Na2Ti6O13 ceramic sintered at 1025 °C were as follows: εr = 34.3, Q×f = 33660 GHz, and τf = 40.3 ppm/°C.

Optimized crystal structure and microwave dielectric properties of BaZnSi3O8‐based ceramics

AbstractIn this study, we synthesized BaZnSi3O8‐based compounds with monoclinic structures (P21/a) using a solid‐state method. The crystal structure, phase composition, and microwave dielectric properties of BaZnSi3O8‐based ceramics were systematically investigated systematically. X‐ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images proved that the maximum solubility of BaZn1‐xMgxSi3O8 ranged between 0.3 and 0.4. Rietveld refinement and Phillips–Van Vechten–Levine complex chemical bond theory were used to illustrate the relationship between the microwave dielectric performance and lattice parameters. To further improve the properties, we substituted Ba2+ with Sr2+ in BaZn0.8Mg0.2Si3O8. Ba1‐ySryZn0.8Mg0.2Si3O8 remained in a single‐phase as y increased from 0 to 1.0. We achieved thermal stability of the resonance frequency of the BaZnSi3O8‐based ceramics by adjusting TiO2 to form composite ceramics. After sintering at 1020°C for 5 h, excellent microwave dielectric properties with εr = 7.44, Q×f = 57,400 GHz, and τf = − 0.2 ppm/°C were realized in the SrZn0.8Mg0.2Si3O8+8 wt %TiO2 system.

Continuing bonds of bereaved Muslims mothers with their young dead child

Based on continuing bonds theory, this research examined the experience and manifestations of continuing bonds of bereaved Muslim mothers with their children who died in home accidents. This qualitative phenomenological study is based on interviews with 15 bereaved mothers (aged 28–46 years) whose children (aged 1–6 years) died 2–7 years before the interviews. Analysis revealed three themes: efforts to continue the physical bonds, challenges in the continuing bonds in cases of traumatic death, and belief in afterlife as the main element of the continuing bonds. The traumatic circumstances of the death challenged the ability to maintain the bond based on positive memories without it being overwhelmed by the traumatic memories of the last moments of the child’s life. Religious beliefs played an important role in the characteristics of the bond. Maintaining the bond requires professionals to provide a therapeutic environment where bereaved mothers feel safe talking about it.

National Pride and the Insecure Social Bond between People and the State: The Socio-emotional Context of National Identity in Post-Soviet Neoliberal Latvia

Abstract This article explores the socio-emotional dimension of national belonging in post-Soviet neoliberal Latvia from the perspective of national pride. I propose this perspective since national pride shapes the character of national belonging. Studies show that national pride in socioeconomic and political attainment is low in post-Soviet countries and Latvia particularly. Influenced by social bond and commitment theories, this study explores why this might be the case by establishing national pride as a relational emotion of national belonging. For understanding national pride it is not enough to explore how people relate to their states. It is also necessary to understand how the states relate to their people, whether they recognize their state constituents, their needs and feel pride in them, and whether they shape social bonds among people. This study explores this question: how does the character of state-society relationship accounts for the low national pride in post-Soviet neoliberal Latvia? To answer, I combine the analysis of the post-Soviet civil discourse and an in-depth exploration of the narratives of 59 emigrants that have left Latvia toward the West in the post-Soviet era. The bonds formed between the Latvian political elite and Western countries during the post-Soviet transformations brought into Latvia neoliberal ideas and policies that, I argue, formed an insecure state-society bond, eroding an opportunity for national pride to flourish and weakening national belonging.

The Challenging World of Simple Inorganic Rings: Revisiting Roesky's Ketone and Roesky's Sulfoxide.

The surprising differences between the experimental solid-state and calculated gas-phase structures of 5-oxo-1,3,2,4-dithiadiazole (Roesky's ketone, 1) and 1-oxo-1,2,4,3,5-trithiadiazole (Roesky's sulfoxide, 2), identified and studied in a series of papers published between 2004 and 2010 but then never satisfactorily explained, have been revisited, making use of the more advanced computational possibilities currently available. The previous calculations' considerable overestimations of the C-S and S-S bond lengths in 1 and 2, respectively, have been partly explained based on the results of periodic calculations and the application of Valence Bond (VB) Theory. In the case of 1, the crystal environment appears to stabilize a structure with a highly polarized C=O bond, which features a C-S bond with considerable double-bond character - an effect which does not exist for the isolated molecule - explaining the much shorter bond in the solid state. For 2, a similar conclusion can be drawn for the S-S distance. For both compounds, though, packing effects are not the sole source of the differences: the inability of Density Functional Theory (DFT) to properly deal with the electronic structures of these apparently simple main-group systems remains a contributing factor.

Crystal structure, bond characterization and lattice energy of B-site 1:3 ordering inverse spinel Li1.25Ga0.25Ti1.5O4 ceramic

In this work, inverse spinel structured Li1.25Ga0.25Ti1.5O4 ceramics with a space group of P4332 were synthesized by a solid-state reaction method. XRD, SAED, HRTEM, and Raman spectra analysis demonstrated that the Li1.25Ga0.25Ti1.5O4 ceramic was formed a A-site 1:3 disordered and B-site 1:3 ordered spinel structured. A high relative density (98.7%) with excellent microwave dielectric properties of εr = 23.8, Q×f = 93,800 GHz, and τf = –21.9 ppm/oC were obtained in 1110 °C for 4 h. Bond valence analysis demonstrated that the average cations of Li1.25Ga0.25Ti1.5O4 were in the rattling state, and the polarizability of Ti4+ was underestimated. The P–V-L chemical bond theory and lattice energy analysis results indicated that B–O bonds were the main factor to affect the εr and Q × f, and the under-bonding Ti4+and Ga3+ has a significant effect on the τf. All the results show that the Li1.25Ga0.25Ti1.5O4 ceramic might be a potential candidate for 5 G communication technology.

Unleashing the potential of Mg2SiO4-based ceramics for millimeter-wave applications: Achieving ultra-low loss with enhanced temperature stability through heterovalent ion substitution

As 5G communication technology advances into millimeter-wave frequencies, the demand rises for microwave dielectric ceramics with low dielectric constant and low dielectric loss. In this regard, Mg2SiO4 emerges as one of the most promising candidates. Herein, Mg2-xGaxSi1-xAlxO4 (MGSA, x = 0∼0.03) ceramics were prepared by a solid-state reaction process employing heterovalent ion substitution strategy, achieving ultra-low loss and enhanced temperature stability of resonant frequency while maintaining low dielectric constant. The effects of the partial substitution of Ga3+ for Mg2+ and Al3+ for Si4+ in MGSA ceramics were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectra, infrared reflectivity spectra, and combined with P–V–L bond theory analysis. XRD results revealed a solid solution formation, while SEM images highlighted microstructure variations with increasing x. Based on P–V–L theory, it was found that the dielectric constant is mainly affected by average bond ionicity Afi, while τf is mainly affected by bond energy E. The intrinsic loss determined Qf value, which is further validated by Raman and infrared spectra. The optimal performance for millimeter-wave applications was achieved at x = 0.01: εr = 6.95, τf = −37.7 ppm/oC, Qf = 244,800 GHz (at 27.15 GHz).

Enforcing Information System Security

Every year brings numerous security breaches that lead to highly destructive ransomware attacks, data leaks, and reputational damage to governments, companies, and other organizations around the world. As a result, there is a growing need to ensure that workers comply with critical policies put in place to avoid such incidents. This study investigated how factors from social bond theory and involvement theory affected compliance with information security policies and procedures. All of the factors examined were found to have a significant influence on attitudes about compliance, and attitude had a significant impact on intention to comply. The findings of this study revealed that it is vital to raise employees' awareness about compliance with security policies by improving their information security behavior. Moreover, all the factors were found to have a significant influence on the attitude of employees towards compliance with their organizational information security policies and procedures.

Comparison of classical and abinitio simulations of hydronium and aqueous proton transfer.

Proton transport in aqueous systems occurs by making and breaking covalent bonds, a process that classical force fields cannot reproduce. Various attempts have been made to remedy this deficiency, by valence bond theory or instantaneous proton transfers, but the ability of such methods to provide a realistic picture of this fundamental process has not been fully evaluated. Here we compare an abinitio molecular dynamics (AIMD) simulation of an excess proton in water to a simulation of a classical H3O+ in TIP3P water. The energy gap upon instantaneous proton transfer from H3O+ to an acceptor water molecule is much higher in the classical simulation than in the AIMD configurations evaluated with the same classical potential. The origins of this discrepancy are identified by comparing the solvent structures around the excess proton in the two systems. One major structural difference is in the tilt angle of the water molecules that accept an hydrogen bond from H3O+. The lack of lone pairs in TIP3P produces a tilt angle that is too large and generates an unfavorable geometry after instantaneous proton transfer. This problem can be alleviated by the use of TIP5P, which gives a tilt angle much closer to the AIMD result. Another important factor that raises the energy gap is the different optimal distance in water-water vs H3O+-water H-bonds. In AIMD the acceptor is gradually polarized and takes a hydronium-like configuration even before proton transfer actually happens. Ways to remedy some of these problems in classical simulations are discussed.

The high of higher education: interactivity its influence and effectiveness on virtual communities

PurposeAmidst the COVID-19 pandemic, education has shifted to online teaching and learning. Interactivity is a crucial tool used to make online education effective. This study empirically examines the role of interactivity in higher education and its influence on students' behavioral outcomes, specifically focusing on soft skills and personality upgradation.Design/methodology/approachA quasi-experimental research design was carried out for post-graduate students undergoing a business communication course from four major institutions. For analysis, t-test, confirmatory factor analysis (CFA) and partial least squares structural equation modeling (PLS-SEM) have been employed. Experimental research has established the causal relationship between interactivity, personality and soft skill upgradation (SSU).FindingsIt was found that the theoretical structural model has a rational model-fit validity. Resultantly, practitioners may use prior knowledge of virtual community (VC) members to enhance web interactivity, thereby increasing social identity and social bonds in a group for more meaningful and effective delivery of online courses.Research limitations/implicationsThe major limitations lie in its context-dependent nature, predominantly influenced by the pandemic-induced mandatory online learning. The study's cross-sectional design also inhibits its ability to assess goal-directed behaviors over time, necessitating further longitudinal research.Originality/valueThe study is one of the pioneering pieces of research that examines the role of pre-defined grouping and enhanced web interactivity in VCs in the context of online learning, especially during the COVID-19 pandemic. Integrating theories of web interactivity, social bond theory (SBT) and social identity theory (SIT) provides a novel understanding of cognitive and social influences that drive meaningful online discussions and their impacts on knowledge enhancement and personality development. Its findings have implications for the design of effective online learning environments and e-learning pedagogy, contributing to the growing domain of information and communication technology (ICT)-enabled education.

Unraveling the Aromatic Rule of Cyclic Superatomic Molecules in π-Conjugated Compounds.

The aromaticity of π-conjugated compounds has long been a confusing issue. Based on a recently emerged two-dimensional (2D) superatomic-molecule theory, a unified rule was built to decipher the aromaticity of cyclic superatomic molecules of π-conjugated compounds from the chemical bonding perspective. Herein, a series of planar [n]helicenes and [n]circulenes, composed of benzene, thiophene, or furfuran, are systemically studied and seen as superatomic molecules ◊On-2◊F2 or ◊On, where superatoms ◊F and ◊O denote π-conjugated units with 5 and 4 π electrons, respectively. The ascertained superatomic Lewis structures intuitively display aromaticity with each basic unit meeting the superatomic sextet rule of benzene, similar to classical valence bond theory, which is favored by the synthesized complex π-conjugated compounds comprising different numbers and kinds of subrings. The evolutionary trend of ring currents and chemical bonding suggests a local ribbon-like aromaticity in these π-conjugated compounds. Moreover, nonplanar helical π-conjugated compounds have the potential to evolve into spring-like periodic materials with excellent physical properties.

Valence Bond Theory Allows a Generalized Description of Hydrogen Bonding.

This paper describes the nature of the hydrogen bond (HB), B:---H-A, using valence bond theory (VBT). Our analysis shows that the most important HB interactions are polarization and charge transfer, and their corresponding sum displays a pattern that is identical for a variety of energy decomposition analysis (EDA) methods. Furthermore, the sum terms obtained with the different EDA methods correlate linearly with the corresponding VB quantities. The VBT analysis demonstrates that the total covalent-ionic resonance energy (RECS) of the HB portion (B---H in B:---H-A) correlates linearly with the dissociation energy of the HB, ΔEdiss. In principle, therefore, RECS(HB) can be determined by experiment. The VBT wavefunction reveals that the contributions of ionic structures to the HB increase the positive charge on the hydrogen of the corresponding external/free O-H bonds in, for example, the water dimer compared with a free water molecule. This increases the electric field of the external O-H bonds of water clusters and contributes to bringing about catalysis of reactions by water droplets and in water-hydrophobic interfaces.

Traditional Values and Adolescent Sexual Orientation in Ethiope East Local Government Area of Delta State, Nigeria

The study investigates the traditional values and sexual orientation of adolescents in secondary school in Delta State. The theoretical frame for the work is the Social Bond Theory. The study is carried out using both quantitative and qualitative research. A descriptive research design and in-depth interviews (IDIs) are used for the study. The study area is the Ethiope East Local Government Area of Delta State. The population of public secondary schools is 26, with about 16,783 senior secondary school students. The sample size is 520 senior secondary school students. The questionnaire titled "Traditional Values and Adolescent Sexual Orientation of Secondary School Students" is used for data collection. It has a reliability of 0.78. A median item is used to answer the research question. The benchmark of acceptance for any item is 2.5, and anything below 2.5 is rejected. The content analysis is applied to the in-depth interviews. Findings from the study revealed that adolescents might not directly support same-sex behaviour due to the traditional values in place emanating from stigma. Also, some students might get involved in same-sex practice if they are opportune to travel out of the country; this implies that the only obstacle to such practice is traditional values. A recommendation was made that parents should educate their children about sexual orientation about our traditional values from infancy until adolescence and stop seeing it as taboo.

Microwave dielectric properties and chemical bond characteristics of low temperature firing Li3VO4 ceramic with low permittivity

Low-fired Li3VO4 ceramics were fabricated and their sintering characteristics, intrinsic structure of the crystal, and microwave dielectric performances were discussed. After the Rietveld refinements, all samples showed the single orthorhombic Li3VO4 phase with the space group Pnm21 over the sintering temperature 700–820 °C for 2–6 h. The results presented that the permittivity, quality factor, and density exhibited a close correlation at different sintering conditions. The homogenous microstructures and outstanding dielectric performances were achieved upon sintering at 730 °C/4h: εr of 6.65, Q × f value of 15,700 GHz, and τf of −103 ppm/°C. The intrinsic characteristics of Li3VO4 compounds were also discussed by chemical bond theory. The results indicated that the V(1)–O bonds dominated the contribution to the dielectric properties of the Li3VO4 ceramics.

Efforts of Class IIA Pekanbaru Women’s Penitentiary in Fulfilling the Rights of Inmates to Interact with Family in the Covid-19 Pandemic

Most of the female prisoners in Pekanbaru Class IIA Women’s Penitentiary have children and families, but while having their sentences, they can’t interact with their children or families as usual. Most of them are mothers. Mothers play an important role in children’s development. The method used in this research is a qualitative method to analyze about how is the efforts of Pekanbaru woman’s penitentiary in optimizing the provision of inmates’ rights by interacting with family during covid-19 pandemic. The results of this study are the efforts of Pekanbaru Class IIA Women’s Penitentiary on granting women’s right is not optimal, which is it is the same as in ordinary penitentiary. There is no special treatment for women in penitentiary even though the interaction with their families, especially their children is very important, considering the children will still need a mother figure. The conclusion of this research is women in penitentiary have a minimum interaction with their families, especially children, and it has the potential to cause children to commit deviate behavior. Based on social bond theory, there are four elements that influence children’s behavior, if any of these elements are not fulfilled then the children will deviate. The children will tend to have no attachment to their parents, especially mothers while the mother is in a penitentiary or prison, and it will cause children to commit delinquency

Theory of singlet fission in carotenoid dimers.

We develop a theory of singlet fission in carotenoid dimers. Following photoexcitation of the "bright" state (i.e., a singlet electron-hole pair) in a single carotenoid, the first step in the singlet fission process is ultrafast intramolecular conversion into the highly correlated "dark" (or 2Ag) state. This state has both entangled singlet triplet-pair and charge-transfer character. Our theory is predicated on the assumption that it is the singlet triplet-pair component of the "dark" state that undergoes bimolecular singlet fission. We use valence bond theory to develop a minimal two-chain model of the triplet-pair states. The single and double chain triplet-pair spectra are described, as this helps explain the dynamics and the equilibrated populations. We simulate the dynamics of the initial entangled pair state using the quantum Liouville equation, including both spin-conserving and spin-nonconserving dephasing processes. By computing the intrachain and interchain singlet, triplet, and quintet triplet-pair populations, we show that singlet fission critically depends on the interchain coupling and the driving potential (that determines endothermic vs exothermic fission).