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Hydrogen production by the catalytic decomposition of ammonia (NH3) is an important process for several important applications, which include energy production and environment-related issues. The role of single Ru-atom substitution in a Cu55 nanocluster (NC) has been illustrated using the NH3 decomposition reaction as a model system. The structural stability of Ru@Cu54 NC has been evaluated using Ru55 and Cu55 NCs for comparison. Ru@Cu54 prefers an icosahedron structure (Ih), like Ru55 and Cu55 NCs, with almost comparable average binding energies of −5.55 eV per atom. The adsorption of NHx (x = 0–3) on different adsorption sites of the icosahedron Ru@Cu54 NC has also been studied and the corresponding adsorption energies have been estimated. The site-preference investigation suggested that NH3 prefers to adsorb vertically to the Ru@Cu54. The stable geometries of the N and H atoms on the high symmetry adsorption sites of Ru@Cu54 NC have been studied. Although the N atom favours top and hollow sites, the H atom prefers to stay in the Ru–Cu bridge site along with the hollow sites. The adsorption energy of N on the Ru@Cu54 NC fcc site is found to be −5.42 eV, which is very close to the optimal value (−5.81 eV) of the ammonia decomposition volcano curve. The reaction energies for stepwise H atom elimination from an adsorbed NH3 molecule have been estimated. Finally, NH3 adsorption and decomposition on Ru@Cu54 have been illustrated in terms of electronic structure analysis. The energetics calculations for the dehydrogenation of NH3 suggest that Ru@Cu54 NC can be a suitable catalyst. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) hydrogenation to formic acid is a promising method for the conversion of CO2 to useful organic products. The interaction of CO2 with hydrogen (H2) on PdmCun (m + n = 4, 8 and 13) clusters to form formic acid (HCOOH) has been explored using density functional theoretical (DFT) calculations. Pd2Cu2, Pd4Cu4 and 13-atom Pd12Cu clusters are found to be the most stable among all of the PdmCun (m + n = 4, 8 and 13) clusters with binding energies of −1.75, −2.16 and −2.40 eV per atom, respectively. CO2 molecules get adsorbed on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters in an inverted V-shaped way with adsorption energies of −0.91, −0.96 and −0.44 eV, respectively. The hydrogenation of CO2 to form formate goes through a unidentate structure that rapidly transforms into the bidentate structure. To determine the transition state structures and minimum energy paths (MEPs) for CO2 hydrogenation to formic acid, the climbing image nudge elastic band (CI-NEB) method has been adopted. The activation barriers for the formation of formic acid from formate on Pd2Cu2 and Pd4Cu4 are calculated to be 0.79 and 0.68 eV, respectively whereas that on the Pd12Cu cluster is 1.77 eV. The enthalpy for the overall process of CO2 hydrogenation to formic acid on the Pd2Cu2, Pd4Cu4 and Pd12Cu clusters are found to be 0.83, 0.48 and 0.63 eV, respectively. Analysis of the density of states (DOS) spectra show that the 4d orbital of Pd, the 3d orbital of Cu, and the 2p orbitals of C and O atoms are involved in the bonding between CO2 molecules and the Pd2Cu2 clusters. The CO2 adsorption on the PdmCun (m + n = 4 and 8) clusters has also been explained in terms of the charge density distribution analysis. [ABSTRACT FROM AUTHOR]

Here, we report the atomic, electronic, and magnetic structures of small ZrmCon (m + n = 2, 4, 6, and 8) alloy clusters based on spin-polarized density functional theory under the plane wave based pseudo-potential approach. The ground state geometry and other low-lying stable isomers of each cluster have been identified using the cascade genetic algorithm scheme. On the basis of the relative energy, it is found that Zr2Co2 (for tetramer), Zr3Co3 (for hexamer), and Zr4Co4 (for octamer) are the most stable isomers than others. In order to underscore the hydrogen storage capacity of these small clusters, the hydrogen adsorption on the stable ZrmCon (m + n = 2, 4, 6, and 8) clusters has also been studied. The electronic structures of ZrmCon clusters with and without adsorbed hydrogen are described in terms of density of states spectra and charge density contours. [ABSTRACT FROM AUTHOR]

Zirconium based alloys have potential applications in automobile, energy and spacecraft industries. The structural, electronic, elastic, vibrational and thermodynamic properties of orthorhombic ZrNi and ZrNiH 3 are studied in detail using the projector augmented wave method and the generalized gradient approximation based on density functional theory. The optimized lattice parameters of both ZrNi and ZrNiH 3 agree well within ±1% from the experimental values. The electronic structure analysis shows significant contribution of 4 d and 3 d orbitals of Zr and Ni to the fermi energy level, respectively and along with signatures of two types of hydrogen atoms occupying the lattice of ZrNiH 3 . Elastic property calculation of these two compounds showed mechanical stability and anisotropy at ambient pressure. In addition, the phonon calculation of both the compounds showed that ZrNi is dynamically stable but ZrNiH 3 is dynamically unstable. The formation energies (Δ f H ) of ZrNi and ZrNiH 3 at 0 K, after zero point energy correction, have been estimated to be −41.87 kJ/mol and −78.25 kJ/mol H 2 , respectively. The temperature dependent thermodynamic functions of ZrNi and ZrNiH 3 have also been calculated from the Debye-Grüneisen quasi-harmonic approximation. [ABSTRACT FROM AUTHOR]

Abstract: The Zr–H system is of particular importance for the solid state storage of hydrogen isotopes in the form of zirconium hydride. Here we report the structural, electronic, vibrational and thermodynamic properties of ZrH2, ZrD2 and ZrT2 using density functional theory (DFT). The structural optimization was carried out by the plane-wave based pseudo-potential method under the generalized gradient approximation (GGA) scheme. The electronic structure of the ZrH2 compound was illustrated explicitly. The vibrational, thermodynamic, and the effect of isotopes on ZrX2 (X = H, D, T) compounds were evaluated by the frozen phonon method. Both the Raman and infrared active vibrational modes of ZrX2 at Γ-point showed significant isotopic effect on ZrX2 compounds. For example, the phonon energy gap between optical and acoustic modes reduces for ZrT2 than ZrD2 and ZrH2. The formation energies of ZrX2 compounds, including the ZPE contributions, were estimated to be −143.68, −147.87 and −150.01 kJ/(mole of compound) for X = H, D and T, respectively. [Copyright &y& Elsevier]

Abstract: The ZrCo intermetallic is considered to be strategically important for hydrogen isotope storage and its use in the International Thermonuclear Experimental Reactor (ITER) system. Here we report the structural, electronic and thermodynamic properties of ZrCo and ZrCoH3 using the first-principles approach. The calculations are performed using a plane-wave based pseudo-potential approach under the framework of spin-polarized density-functional theory. The ground state properties like lattice constants, bulk moduli, and enthalpy of formation have been determined by optimizing the atomic and electronic structure of ZrCo and ZrCoH3 compounds. From the total energy calculations, the enthalpy of formation of ZrCoH3 from ZrCo is estimated to be −91 kJ/mol H2 at 0 K. Both lattice parameters and formation energy are found to be in good agreement with their corresponding experimental values. The nature of chemical bonding in ZrCo and ZrCoH3 has been analyzed from the electronic density of states spectrum of the constituent materials. [Copyright &y& Elsevier]

Hydrogen production by the catalytic decomposition of ammonia (NH 3 ) is an important process for several important applications, which include energy production and environment-related issues. The role of single Ru-atom substitution in a Cu 55 nanocluster (NC) has been illustrated using the NH 3 decomposition reaction as a model system. The structural stability of Ru@Cu 54 NC has been evaluated using Ru 55 and Cu 55 NCs for comparison. Ru@Cu 54 prefers an icosahedron structure ( I h ), like Ru 55 and Cu 55 NCs, with almost comparable average binding energies of -5.55 eV per atom. The adsorption of NH x ( x = 0-3) on different adsorption sites of the icosahedron Ru@Cu 54 NC has also been studied and the corresponding adsorption energies have been estimated. The site-preference investigation suggested that NH 3 prefers to adsorb vertically to the Ru@Cu 54 . The stable geometries of the N and H atoms on the high symmetry adsorption sites of Ru@Cu 54 NC have been studied. Although the N atom favours top and hollow sites, the H atom prefers to stay in the Ru-Cu bridge site along with the hollow sites. The adsorption energy of N on the Ru@Cu 54 NC fcc site is found to be -5.42 eV, which is very close to the optimal value (-5.81 eV) of the ammonia decomposition volcano curve. The reaction energies for stepwise H atom elimination from an adsorbed NH 3 molecule have been estimated. Finally, NH 3 adsorption and decomposition on Ru@Cu 54 have been illustrated in terms of electronic structure analysis. The energetics calculations for the dehydrogenation of NH 3 suggest that Ru@Cu 54 NC can be a suitable catalyst.

Carbon dioxide (CO 2 ) hydrogenation to formic acid is a promising method for the conversion of CO 2 to useful organic products. The interaction of CO 2 with hydrogen (H 2 ) on Pd m Cu n ( m + n = 4, 8 and 13) clusters to form formic acid (HCOOH) has been explored using density functional theoretical (DFT) calculations. Pd 2 Cu 2 , Pd 4 Cu 4 and 13-atom Pd 12 Cu clusters are found to be the most stable among all of the Pd m Cu n ( m + n = 4, 8 and 13) clusters with binding energies of -1.75, -2.16 and -2.40 eV per atom, respectively. CO 2 molecules get adsorbed on the Pd 2 Cu 2 , Pd 4 Cu 4 and Pd 12 Cu clusters in an inverted V-shaped way with adsorption energies of -0.91, -0.96 and -0.44 eV, respectively. The hydrogenation of CO 2 to form formate goes through a unidentate structure that rapidly transforms into the bidentate structure. To determine the transition state structures and minimum energy paths (MEPs) for CO 2 hydrogenation to formic acid, the climbing image nudge elastic band (CI-NEB) method has been adopted. The activation barriers for the formation of formic acid from formate on Pd 2 Cu 2 and Pd 4 Cu 4 are calculated to be 0.79 and 0.68 eV, respectively whereas that on the Pd 12 Cu cluster is 1.77 eV. The enthalpy for the overall process of CO 2 hydrogenation to formic acid on the Pd 2 Cu 2 , Pd 4 Cu 4 and Pd 12 Cu clusters are found to be 0.83, 0.48 and 0.63 eV, respectively. Analysis of the density of states (DOS) spectra show that the 4d orbital of Pd, the 3d orbital of Cu, and the 2p orbitals of C and O atoms are involved in the bonding between CO 2 molecules and the Pd 2 Cu 2 clusters. The CO 2 adsorption on the Pd m Cu n ( m + n = 4 and 8) clusters has also been explained in terms of the charge density distribution analysis.

The paper explores how the experiences of the present pandemic are shaped by the memories of popular religious piety during past pandemics and epidemics. Taking insights from the works of Astrid Erll and Reinhart Koselleck, the process 'remembering-imagining system' within the context of the pandemic is discussed by tracing the reemergence of pandemic deities and narratives of piety in India. Using digitally documented and disseminated narratives on piety emerging during COVID-19, an attempt is made to understand how these narratives shape the experiences, responses, and collective memory of the pandemic. Through a discussion of the shift in the imagination of political leadership and the moral responsibilities of the community, an attempt is made to highlight the mode in which the narratives on piety shape the contours of a time that is otherwise unimaginable. The mediated memories of popular religious piety make it possible to remember similar crisis times and to imagine and reinstate the social order that is threatened by this sudden unimaginable crisis. The paper thus argues that within the context of India, popular religious piety, though often overlooked, becomes a significant part of making sense and shaping the experiences of the pandemic time., Competing Interests: Competing InterestsThe authors declare no competing interests., (© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2022.)