Bond Index Research Articles

Fe Crystalline Phases in Fe/C Composites Modulated the Selective Adsorption of Pb(II) from Industrial Wastewater with Cd(II): An Electronic-Scale Perspective.

Fe oxide or Fe0-based materials display weak removal capacity for Pb(II), especially in the presence of Cd(II), and the electronic-scale mechanisms are not reported. In this study, Fe3C(220) modified black carbon (BC) [Fe3C(220)@BC] with high adsorption and selectivity for Pb(II) from industrial wastewater with Cd(II) was developed. The quantitative experiment suggested that Fe species accounted for 80.5-100 and 18.4-33.8% of Pb(II) and Cd(II) removal, respectively. Based on X-ray absorption near-edge structure analysis, 57.3% of adsorbed Pb2+ was reduced to Pb0; however, 61.6% of Cd2+ existed on Fe3C@BC. Density functional theory simulation unraveled that Cd(II) adsorption was attributed to the cation-π interaction with BC, whereas that of Pb(II) was ascribed to the stronger interactions with different Fe phases following the order: Fe3C(220) > Fe0(110) > Fe3O4(311). Crystal orbital bond index and Hamilton population analyses were innovatively applied in the adsorption system and displayed a unique discovery: the stronger Pb(II) adsorption on Fe phases was mediated by a combination of covalent and ionic bonding, whereas ionic bonding was mainly accounted for Cd(II) adsorption. These findings open a new chapter in understanding the functions of different Fe phases in mediating the fate and transport of heavy metals in both natural and engineered systems.

GREEN BOND INDEX PRICE FORECASTING: COMPARATIVE ANALYSIS OF MACHINE LEARNING MODELS

Today, green financial products have garnered recognition and are consequently regarded as alternative assets. Green bonds exclusively allocate their funds to environmentally sustainable initiatives. Green bonds facilitate companies in enhancing both their financial and environmental performance by promoting innovations stemming from green initiatives and long-term green investments. This study focused on predicting the price of the green bond index in Japan. The input factors for price prediction in Japan include Nikkei225, USD/JPY, and crude oil price assets, which are seen as alternative investment options for Japanese investors. The study utilized a dataset spanning 693 days, from 06.05.2021 to 02.05.2024. The acquired data is partitioned into two distinct sets: one for training and one for testing. 80% of the data was allocated for training purposes, while the remaining 20% was designated for testing. The study utilized various prediction approaches including RF, MLP, GBR, XGBoost, LSTM, SVR, Catboost, and Linear Regression. The performance of these models was compared using evaluation metrics such as MSE, RMSE, MAE, MAPE, and R2 values. The research revealed that the GBR model exhibited the highest performance on the training data set, whereas the XGBoost and RF models yielded superior prediction results on the test data set.

Study of heavy metals adsorption using a silicate-based material: Experiments and theoretical insights

Heavy metal toxicity in water is a serious problem with harmful effects on human health and the ecosystem. This research studied a silicate-based material as an adsorbent for removing four heavy metals from aqueous solutions. The target metal pollutants selected include manganese (Mn2+), copper (Cu2+), cobalt (Co2+), and zinc (Zn2+). First, theoretical tools including potential energy surface analysis, Natural Population Analysis, AIM, Wiberg Bond Index, QTAIM, and topological methods offer profound insights into the nature of interactions present in the Mg2O8Si3M (M = Mn2+, Cu2+, Co2+, Zn2+) clusters. Second, the synthesis and characterization of eco-friendly hydrated amorphous magnesium silicate (MgOSiO2nH2O) was developed. Last, a simple kinetic adsorption test was applied to assess the material selectivity towards heavy metals and support theoretical results. The kinetic adsorption study was analyzed through the pseudo-first and second-order kinetics, Elovich, and the intraparticle diffusion models. The theoretical analysis of the adsorption energies indicates that the adsorption of four metal ions on the Mg2O8Si3 surface is energetically favorable in all cases. The material displayed the following adsorption sequence: Cu2+ (59 mg g-1) > Zn2+(25 mg g-1) ≈ Co2+ (23 mg g-1) > Mn2+ (15 mg g-1). This knowledge can then be used to design and optimize low-cost silicate-based materials for effective heavy metal removal, contributing to efforts to address environmental pollution and protect public health.

Catalytic Activity of an Asymmetric Uranyl‐Salophen on 2,4‐Dichlorophenol, 2,4,6‐Trichlorophenol, and Pentachlorophenol

ABSTRACTThis study employs density functional theory to investigate whether asymmetric uranyl‐Salophen catalyzes the activation of 2,4‐dichlorophenol, 2,4,6‐trichlorophenol, and pentachlorophenol. Changes in various important parameters such as bond lengths, Wiberg bond indices, infrared vibrational absorption spectra, natural charge distributions, ultraviolet–visible absorption spectra, and 13C NMR chemical shifts of the aromatic rings of chlorophenols before and after forming complexes with asymmetric uranyl‐Salophen are analyzed. This means that asymmetric uranyl‐Salophen indeed activates 2,4‐dichlorophenol, 2,4, 6‐trichlorophenol, and pentachlorophenol, significantly lengthening the aromatic ring bonds of the three chlorophenols and increasing the electrophilicity of the carbon atoms in the aromatic ring. This suggests that the conjugated system of the aromatic ring is also partially disrupted, indicating that these three chlorophenols are indeed catalytically activated. Furthermore, this implies that this asymmetric uranyl‐Salophen may be used to degrade chlorophenols in water.

Predicting Small Molecule Activations Including Dinitrogen Based on an Inorganic Benzene B4N2 Framework.

Although main group species have emerged in the field of dinitrogen activation in recent years, the reported examples are particularly rare in comparison with transition metal complexes due to their significant challenges. Herein, we demonstrate a [4 + 2] cycloaddition reaction of N2 (with an activation energy as low as 12.5 kcal mol-1) initiated by an inorganic benzene via density functional theory calculations. Such N2 activation is supported by the elongated nitrogen-nitrogen bond distance (dNN), decreased vibration frequency (νNN), and weakened Wiberg bond index (WBINN). Subsequently, the "push-pull" electronic effect, formed by introducing a Lewis acid, HB(C6F5)2, facilitates the generation of thermodynamically more stable products. In addition, this inorganic benzene could also be used to activate a series of small molecules, including carbon dioxide, acetylene, ethylene, and acetonitrile with reaction barriers ranging from 4.7 to 11.6 kcal mol-1. Our findings provide an alternative approach to N2 activation and functionalization, theoretically validating the feasibility of the dual Lewis acid strategy for dinitrogen activation.

β-d-Glucopyranose – Silver+ (1:1) complex assisted aromaticity involving electron deficient X3 (X=Be, Mg) core

Seeing the frontier molecular orbitals (FMO) picture of β-d-glucopyranose–silver+ (1:1) complex ([Ag(C6H12O6)]+) reported in a recent article (Mondal, 2024) [53], we used the FMO based approach to obtain inverted sandwich like organometallic complex comprising X3 (X=Be, Mg) core, in silico. Thermodynamic feasibility of obtaining [(C6H12O6)Ag-X3-Ag(C6H12O6)] (X=Be, Mg) complexes are explored. Conceptual density functional theory (CDFT) based reactivity descriptors guide to ascertain the stability order of such complexes. By the help of natural bond orbital analysis, Wiberg bond indices (WBI), bond critical point analysis, electron density descriptors, and gradient isosurface between selected contacts, the nature of interaction between the X3 core and Ag metals are studied. FMO of the complexes further help in ascertaining the nature of binding. Energy decomposition analysis marks the interaction between X3 and Ag metals in [(C6H12O6)Ag-X3-Ag(C6H12O6)] (X=Be, Mg) as partially covalent. Negative values of nucleus independent chemical shift (NICS) at the triangular ring (X3) centres [NICS(0)] indicate aromatic property.

Complex non-linear relationship between conventional and green bonds: Insights amidst COVID-19 and the RU–UA conflict

In times of crisis, such as global pandemics or conflicts, investors’ preference between green and conventional bonds may lean towards the latter due to increased risk aversion and a focus on short-term stability. However, some investors motivated by increased awareness of sustainability issues may maintain or increase their allocation to green bonds, seeing them as an opportunity for long-term resilience and sustainable investing. We use multifractal detrended cross-correlation analysis, wavelet coherence, and copula-based dependence analysis to examine the complex relationship between the S&P Green Bond Index and the S&P 500 Bond Index. The results indicate the presence of multifractal cross-correlations, the strength of which is most pronounced in times of crisis, especially in the post-COVID-19 period. The wavelet-based analysis also detects the COVID-19 break and shows significant interdependence at all frequency levels after the RU–UA conflict. The copula-based correlation values exhibit a distinct oscillating pattern over time, characterized by an initial break coinciding with the impact of COVID-19. In light of these findings on the impact of COVID-19 and the RU–UA conflict, we have included the Geopolitical Risk Index in our analysis to better understand how geopolitical tensions and conflicts influence the observed interdependence and to gain insight into how changes in the global risk environment affect both bond market dynamics. Overall, the results of this study provide insights into the interconnectedness between conventional and green bond markets and highlight potential spillover effects and systemic risks in an increasingly complex financial landscape.

Solvent effects on the structures of the hydrated copper dication clusters

Understanding the solvation process requires an understanding of how the solvent affects the molecular cluster configurations. The current study examined the impact of solvents on the structures of the hydrated Cu2+ cation, as well as the temperature dependence, and the energetics of the hydrated Cu2+ cation clusters from sizes n=1 from n=10 (Cu2+(H2O)n=1−10). The potential energy surfaces (PESs) in the solvent phase (represented by a dielectric continuum medium) at the MP2/6-31++G(d,p) level of computation have been comprehensively investigated. We employed the integral equation formalism polarized continuum model (IEF-PCM) to describe the dielectric continuum medium. It is pointed out that changes in PESs of hydrated copper dication isomers and structural morphologies occur in the continuum medium. Thus, the relative energies are smallest at T=0 K and for the cluster populations of Cu2+(H2O)n=1−10 are modified. Thus, in the solvent phase, the competition between the conformers is more severe than in the gas phase. Furthermore, highly coordinated conformers are more favorable, and favored conformers in the gas phase are disfavored in the solvent phase. The structural investigations are validated by the analysis of Wiberg Bond Index (WBI) at 300 K. In the solvent phase, the WBIs of the most stable isomers are the smallest and the WBIs of axial bonds are lower than those of equatorial bonds. Concerning the energy analysis, the binding energies were predicted for enormous sizes (at saturation) using a fit function. Thus, the new values of the binding energies obtained are -5467.8 and ▪ in the gas and solvent phases respectively. All these observed differences are due to the effects of the implicit solvent.

THE IMPACT OF THE RECIPROCAL RELATIONSHIP BETWEEN EXCHANGE RATES AND INTEREST RATES ON THE BOND MARKET USING THE SVAR MODEL FOR CHINA FOR THE PERIOD FROM (2000-2020)

This study aims to illustrate the effect of the reciprocal relationship between the exchange rates and interest rates on the bond market by using the SVAR model for China during (2000 -2020), this is to analyze and measure the relationship between exchange rates and interest rates and showing their impact through changes in the bond index and monitoring the changes that occur in their traded prices in the financial markets. This study is based on three standard model estimations. The first model includes the effect of interest rates and inflation on the exchange rates. The second model shows the effect of the exchange rates and money supply on the interest rate. The third model includes the effect of exchange and interest rates on the bond index. The Structural Vector Auto Regression Model (SVAR) was used to test the long-term relationship between the variables of the study, in addition to the variance Decomposition analysis and the analysis of the Impulse response functions (IRF). The results showed that the reciprocal relationship between the exchange rates and interest rates is a positive inverse relationship, and the effect is in both directions. In other words, when the prevailing interest rate rises in the country, it leads to an appreciation in the value of the currency due to the increase in demand for the currency of that country, resulting in a depreciation in its exchange rate and conversely. In addition, the results indicated that the bond index is sensitive to any shock or any unexpected change in exchange rate and interest rate and that these shocks manifest in the short term and stabilize in the long term.

The impact of refinancing transaction policy adjustment on stock market volatility

This paper investigates the impact of refinancing transaction policy adjustment on the volatility of convertible bond market. Through GARCH model analysis, it is found that the refinancing policy adjustment significantly affects the spillover effect between CSI 300 index and CSI convertible bond index, indicating that the policy adjustment leads to differences in the speed of market reaction to common information and the degree of change in yield, which reflects the market's sensitivity to the policy change as well as the adaptability of market participants. The empirical results show that the convertible bond market has a significant dynamic impact on the stock market during the policy adjustment period, accompanied by the improvement of market efficiency, which supports the hypothesis that the refinancing policy adjustment has a significant impact on the spillover effect between the two markets.

Effects of the utilization of green bonds proceeds on green bond premium

The measurement of premium remains a major challenge in the literature. This study explores the effects of green bond usage on green bond premium using green bonds data extracted from Bloomberg MSCI green bond index between 2007 and 2022. The study leverages fixed effects and pooled regression models to examine whether the green bond premium varies systematically with the issuer's specified use of the green bond's proceeds. The empirical results provide evidence of a positive association between the use of proceeds of green bonds and the premium on green bonds. The green premium of an average of 1–5 basis points across government and corporate issuers is observed. Our findings not only establish the influence of green bond usage on green premium, but also provides further evidence of how issuers can achieve borrowing cost advantage if the proceeds are targeted at environmentally friendly projects that align with investor preferences.

Exploring the Nature of Ag–Ag Interactions in Different Tellurides by Means of the Crystal Orbital Bond Index (COBI)

Exploring the Nature of Ag–Ag Interactions in Different Tellurides by Means of the Crystal Orbital Bond Index (COBI)

Formation of Delocalized Linear M-B-M Covalent Bonds: A Combined Experimental and Theoretical Study of BM2(CO)8+ (M = Co, Rh, Ir) Complexes.

Investigations of transition-metal boride clusters not only lead to novel structures but also provide important information about the metal-boron bonds that are critical to understanding the properties of boride materials. The geometric structures and bonding features of heteronuclear boron-containing transition metal carbonyl cluster cations BM(CO)6+ and BM2(CO)8+ (M = Co, Rh, and Ir) are studied by a combination of the infrared photodissociation spectroscopy and density functional calculations at B3LYP/def2-TZVP level. The completely coordinated BM2(CO)8+ complexes are characterized as a sandwich structure composed of two staggered M(CO)4 fragments and a boron cation, featuring a D3d symmetry and 1Eg electronic ground state as well as metal-anchored carbonyls in an end-on manner. In conjunction with theoretical calculations, multifold metal-boron-metal bonding interactions in BM2(CO)8+ complexes involving the filled d orbitals of the metals and the empty p orbitals of the boron cation were unveiled, namely, one σ-type M-B-M bond and two π-type M-B-M bonds. Accordingly, the BM2(CO)8+ complexes can be described as a linear conjugated (OC)4M═B═M(CO)4 skeleton with a formal B-M bond index of 1.5. The three delocalized d-p-d covalent bonds render compensation for the electron deficiency of the cationic boron center and endow both metal centers with the favorable 18-electron structure, thus contributing much to the overall structural stability of the BM2(CO)8+ cations. As a comparison, the saturated BRh(CO)6+ and BIr(CO)6+ complexes are determined to be a doublet Cs-symmetry structure with an unbridged (OC)2B-M(CO)4 pattern, involving a two-center σ-type (OC)2B → M(CO)4+ dative single bond along with a weak covalent B-M half bond. This work offers important insight into the structure and bonding of late transition metal boride carbonyl cluster cations.

Unexpected Ag-H bond in the predictive silver hydride phase under high pressure

Silver, typically acknowledged for its inertness toward hydrogen under standard conditions, exhibits a noteworthy shift in reactivity under elevated pressures. Employing first-principles variable-composition evolutionary search calculations, our investigation unveils the presence of thermodynamically stable Ag-H compounds. A novel stoichiometry, Ag2H, characterized by P3¯m1 symmetry, emerges as the thermodynamically stable phase at 100 GPa. Notably, the trigonal-Ag2H phase at 100 GPa demonstrates both mechanical and dynamic stability, as ascertained through the computation of elastic constants and phonon dispersions, respectively. Examination of the electronic band structure and density of states manifests the metallic nature of the resulting Ag2H compound. A comprehensive analysis involving crystal orbital bond index, Bader charge, and charge density plots substantiates the ionic character of Ag2H, attributable to effective charge transfer from silver atoms to hydrogen. Furthermore, application of the Allen-Dynes modified McMillan equation indicates the absence of superconducting behavior in Ag-H systems at the elevated pressure of 100 GPa.

Are clean energy markets hedges for stock markets? A tail quantile connectedness regression

Acknowledging the long-term potential of alternative energy sources, this paper examines the quantile frequency connectedness between clean energy markets and international stock markets, with implications related to hedging effectiveness. The main results point out that spillovers run from the US, the EU, the UK, and the Renewable Energy and Clean Technology Index to Japan and the Global Clean Energy Index. Furthermore, while the transmissions are concentrated in the short run during normal (0.5) and bull market (0.95) conditions, they extend to intermediate and long-term amid busting market (0,05 quantile) states, signifying a long-lasting impact that cannot be absorbed in the short run. Notably, clean energy index roles in information transmissions range from a net sender (Renewable Energy and Clean Technology Index), isolated (Green Bond Index), and a net receiver (Global Clean Energy Index). From a multivariant portfolio design perspective, we notice that a substantial weight should be allocated to clean energy assets, WTI, and CSI300 when compared with the rest of the financial markets. Moreover, the low (high) volatility regime yields lower (higher) weights than the ones reported in the mean state, but the results remain largely similar. Bivariant portfolio weights show that GB should have substantial weight when paired with all assets.

Connectedness between Sustainable Investment Indexes: The QVAR Approach

We studied the relationship between sustainable investment indexes and examine whether this relationship varies in bullish, bearish, and stable financial markets. To understand this issue more deeply, we analyzed the connectedness between three indexes—the Sustainable Impact investments, Paris-aligned stocks, and green bonds indexes—using the daily closing prices from 1 June 2017 to 15 April 2024, encompassing 1793 observations. We used a quantile vector autoregressive (QVAR) model to understand the dynamic relationship among the considered indices. The findings indicate that sustainable investments are strongly interconnected in both high and low quantiles, but this connection weakens significantly during periods of market stability. The Sustainable Impact investments and Paris-aligned stocks indexes are net transmitters of impacts to other sustainable alternatives, while the green bonds index is a net receiver. We also observed an increase in interconnectedness across all quantiles during the pandemic, the Russia–Ukraine military conflict, and changes in the European Union and the United States’ monetary policies.

A Fundamental Perspective on the Selective Zn Substitution in Ternary Ordered Intermetallic Compound Cu6Zn2Sb2

AbstractThe unique site substitution of Zn in the structure of tetragonal and atomically ordered Cu6Zn2Sb2, followed by the formation of Cu5Zn3Sb2, has been addressed from fundamental perspectives. First principles energy calculations, and semi‐empirical electronic structure calculations using the density of states, crystal orbital Hamilton population, crystal orbital bond index and Mulliken population analysis were performed to understand the observed substitution pattern and the narrow homogeneity range of the titled compound. Mulliken and Löwdin's approach of charge analysis explain the experimentally proved ‘coloring’, based on the ‘site energy’ argument. The concept of ‘topological charge stabilization’ has been introduced in this context. Valence electron concentration and the optimization of the partially covalent Cu−Sb interactions also play pivotal role in the electronic stability of the titled phase.

Dynamic impact of the US yield curve on green bonds: Navigating through recent crises

We examine the effect of the US yield curve on the global green bond markets at the forefront of the climate change fight. For this purpose, we compute three components (level, slope, and curvature) of the US yield curve based on daily data of the treasury yields with several maturities from January 2009 to June 2022 and employ country-level S&P green bond indices. Our dynamic network analysis shows that the level component of the yield curve is more influential in transmitting return and volatility shocks to green bonds, while curvature is primarily absorptive. The European, the US, and Hong Kong green bonds are the leading players in shock propagation. Both return- and volatility spillovers are time-varying and remain high during periods of systemically important events, especially COVID-19 and the Russia-Ukraine war, supporting the Global Financial Cycle Hypothesis. The war also changes the net behaviors (transmitter versus receiver) of the components and the indices. Investors and issuers of green bonds are advised to keenly observe the shape of the US yield curve and systemic events for better decision-making regarding investment horizons and contagion risk management.

First principles study on interactions in inorganic molecular crystals at zero dimensions

Inorganic molecular crystals (IMCs) are attracting significant scientific interest due to their distinctive anisotropic crystal structure. The molecular units in the form of cages are the fundamental unit of these materials and most of their properties are dependent on the geometry, their arrangement and the interactions present in between these cages. This work is carried out to shed light on the structural arrangement and the interaction properties of three IMCs including antimony oxide (Sb2O3), phosphorous tri-selenium (P4Se3) and phosphorous trioxide (P4O6) in zero dimensions. The reported calculations were carried out using density Functional Theory (DFT) to investigate the interactions between the cages based on ETS-NOCV, NBO, Wiberg bond indices and QTAIM analysis. The results revealed weak VdWs association along the inter-cages and significant covalent bonding within the cage. The investigation shows that Sb2O3 and P4Se3 IMCs have potential applications in high-pressure and stress-bearing materials.

Green bonds forecasting: evidence from pre-crisis, Covid-19 and Russian–Ukrainian crisis frameworks

PurposeWithout precedent, green bonds confront, for the first time since their emergence, a twofold crisis context, namely the Covid-19-Russian–Ukrainian crisis period. In this context, this paper aims to investigate the connectedness between the two pioneering bond market classes that are conventional and treasury, with the green bonds market.Design/methodology/approachIn their forecasting target, authors use a Support Vector Regression model on daily S&P 500 Green, Conventional and Treasury Bond Indexes for a year from 2012 to 2022.FindingsAuthors argue that conventional bonds could better explain and predict green bonds than treasury bonds for the three studied sub-periods (pre-crisis period, Covid-19 crisis and Covid-19-Russian–Ukrainian crisis period). Furthermore, conventional and treasury bonds lose their forecasting power in crisis framework due to enhancements in market connectedness relationships. This effect makes spillovers in bond markets more sensitive to crisis and less predictable. Furthermore, this research paper indicates that even if the indicators of the COVID-19 crisis have stagnated and the markets have adapted to this rather harsh economic framework, the forecast errors persist higher than in the pre-crisis phase due to the Russian–Ukrainian crisis effect not yet addressed by the literature.Originality/valueThis study has several implications for the field of green bond forecasting. It not only illuminates the market participants to the best market forecasters, but it also contributes to the literature by proposing an unadvanced investigation of green bonds forecasting in Crisis periods that could help market participants and market policymakers to anticipate market evolutions and adapt their strategies to period specificities.