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Investigation reveals that the Al4 unit in neutral Al4Na4 and anion Al4Na3 (super -) clusters has 4n Pi electrons and has a rectangular structure with alternate Pi bonds. Neutral Al4Na4 and anion Al4Na3 (super -) clusters satisfy the criteria for antiaromaticity and are metallo-antiaromatic compounds.

The coordinatively unsaturated chromium(II)‐based Cr3[(Cr4Cl)3(BTT)8]2 (Cr−BTT; BTT3−=1,3,5‐benzenetristetrazolate) metal–organic framework (MOF) has been shown to exhibit exceptional selectivity towards adsorption of O2 over N2/H2. Using periodic density functional theory (DFT) calculations, we attempted to decipher the origin of this puzzling selectivity. By computing and analyzing the magnetic exchange coupling, binding energies, the partial density of states (pDOS), and adsorption isotherms for the pristine and gas‐bound MOFs [(Cr4(X)4Cl)3(BTT)8]3− (X=O2, N2, and H2), we unequivocally established the role of spin states and spin coupling in controlling the gas selectivity. The computed geometries and gas adsorption isotherms are consistent with the earlier experiments. The binding of O2 to the MOF follows an electron‐transfer mechanism resulting in a CrIII superoxo species (O2.−) with a very strong antiferromagnetic coupling between the two centers, whereas N2/H2 are found to weakly interact with the metal center and hence only slightly perturb the associated coupling constants. Although the gas‐bound and unbound MOFs have an S=0 ground state (GS), the nature of spin the configurations and the associated magnetic exchanges are dramatically different. The binding energy and the number of oxygen molecules that can favorably bind to the Cr center were found to vary with respect to the spin state, with a significant energy margin (47.6 kJ mol−1). This study offers a hitherto unknown strategy of using spin state/spin couplings to control gas adsorption selectivity in MOFs. [ABSTRACT FROM AUTHOR]

The steadiness of Lewis acid-base complexes using the hard-soft acid-base (HSAB) technique is discussed. The major function of the electronegativity equalization and the charge redistribution process in stabilizing the complexes is established.

Research has been conducted on the Wolff rearrangements of alpha-diazaketones. Results indicate that microwave irradiation of these diazaketones promotes Wolff rearrangement via the Z-configurations.

The first theoretical study of molecular recognition of systems interacting via multiple sites, using the density response functions is presented. This model can be used as a predictive tool for understanding general molecular interaction.

An examination is done on the density functional theory (DFT) descriptors, which have been used to explain 'intermolecular' reactivity. The concept of group softness is seen to be efficient for both types of charge partitioning used and all of the basis sets used for the research.

Research is presented describing the use of reactivity descriptors to study weak adsorption of gaseous molecules in the zeolite lattice. Focus is given to local hard-soft acid-base principle and Fukui function-based descriptors.

Research was conducted to examine the impact of isomorphous substitution of Si by Al, Ga and B in the tetrahedral sites of a zeolite framework on the characteristics of Bronsted acid sites using computational methods. The density functional theory based acidity descriptor 'local softness' and a new acidity descriptor 'relative electrophilicity' were used to predict the acidity sequence of the zeolite clusters. Results demonstrate that the acidity trend obtained from the relative electrophilicity follows the experimental trend.

The open-shell reference relativistic equation-of-motion coupled-cluster method within its four-component description is successfully implemented with the consideration of single- and double- excitation approximations using the Dirac-Coulomb Hamiltonian. At the first attempt, the implemented method is employed to calculate ionization potential value of heavy atomic (Ag, Cs, Au, Fr, and Lr) and molecular (HgH and PbF) systems, where the effect of relativity does really matter to obtain highly accurate results. Not only the relativistic effect but also the effect of electron correlation is crucial in these heavy atomic and molecular systems. To justify the fact, we have taken two further approximations in the four-component relativistic equation-of-motion framework to quantify how the effect of electron correlation plays a role in the calculated values at different levels of theory. All these calculated results are compared with the available experimental data as well as with other theoretically calculated values to judge the extent of accuracy obtained in our calculations. [ABSTRACT FROM AUTHOR]

Auger decay is an efficient ultrafast relaxation process of core-shell or inner-shell excited atom or molecule. Generally, it occurs in femto-second or even atto-second time domain. Direct measurement of lifetimes of Auger process of single ionized and double ionized inner-shell state of an atom or molecule is an extremely difficult task. In this paper, we have applied the highly correlated complex absorbing potential-equation-of-motion coupled cluster (CAP-EOMCC) approach which is a combination of CAP and EOMCC approach to calculate the lifetime of the states arising from 2p inner-shell ionization of an Ar atom and 3d inner-shell ionization of Kr atom. We have also calculated the lifetime of Ar2+(2p-13p-1)¹D, Ar2+(2p-13p-1)¹S, and Ar2+(2p-13s-1) 1P double ionized states. The predicted results are compared with the other theoretical results as well as experimental results available in the literature. [ABSTRACT FROM AUTHOR]

We propose a new elegant strategy to implement third order triples correction in the light of many-body perturbation theory to the Fock space multi-reference coupled cluster method for the ionization problem. The computational scaling as well as the storage requirement is of key concerns in any many-body calculations. Our proposed approach scales as N6 does not require the storage of triples amplitudes and gives superior agreement over all the previous attempts made. This approach is capable of calculating multiple roots in a single calculation in contrast to the inclusion of perturbative triples in the equation of motion variant of the coupled cluster theory, where each root needs to be computed in a state-specific way and requires both the left and right state vectors together. The performance of the newly implemented scheme is tested by applying to methylene, boron nitride (B2N) anion, nitrogen, water, carbon monoxide, acetylene, formaldehyde, and thymine monomer, a DNA base. [ABSTRACT FROM AUTHOR]

The equation-of-motion coupled cluster method employing the complex absorbing potential has been used to investigate the low energy electron scattering by CO2. We have studied the potential energy curve for the 2∏u resonance states of CO2- upon bending as well as symmetric and asymmetric stretching of the molecule. Specifically, we have stretched the C-O bond length from 1.1 Å to 1.5 Å and the bending angles are changed between 180° and 132°. Upon bending, the low energy 2∏u resonance state is split into two components, i.e., ²A1, ²B1 due to the Renner-Teller effect, which behave differently as the molecule is bent. [ABSTRACT FROM AUTHOR]

We make sharp estimates to obtain a Schwarz-type lemma for the symmetrized polydisc G n and for the extended symmetrized polydisc G ~ n . We explicitly construct an interpolating function under certain condition. To do so, we followed the methods described in [Young NJ. The automorphism group of the tetrablock. J Lond Math Soc. 2008;77(2):757–770]. Also we find a few geometric interplay between the members of the family G ~ n and its closure Γ ~ n . [ABSTRACT FROM AUTHOR]