We have demonstrated an application of a stationary coupled cluster response approach for molecular properties using an Euler functional. This involves terms which are of cubic power in cluster amplitudes. We have shown that these are important terms and have also discussed the convergence properties of the functional for higher order properties.

Molecular orbital calculations (EHMO) have been performed on five ruthenium carbonyl clusters considered to be involved in the reductive carbonylation of nitrobenzene. The bonding in the isocyanate cluster, [HRu₃(CO)₉(HNCO)]⁻, is shown to arise mainly from the interaction between the LUMO of HNCO and HOMO of the [HRu₃(CO)₉]⁻ fragment. The relative stabilities of this cluster, two of its isomers and the CO-eliminated cluster [HRu₃(CO)₉(HN)]⁻, are also commented upon. The calculated results are in accordance with empirical kinetic data.

The size-dependence of different local reactivity descriptors of dimer A₂ and AB type of systems is discussed. We derive analytic results of these descriptors calculated using finite difference approximation. In particular, we studied Fukui functions, relative electrophilicity and relative nucleophilicity, local softness and local philicity. The results are explained using the example of the dimer of BH₃NH₃.

In this paper, we study the reactivity of diimines like 2,2'-bipyridine and its analogues using reactivity descriptors. We discuss evaluation of local descriptors using relaxed as well as frozen approximation and characterize the 𝜎/𝜋 acceptance/donor characteristics of the above ligands. The intermolecular reactivity sequence for the same systems is examined by the global and local philicity index. In addition, electron density analysis has been carried out to highlight the possible strengths of interaction of the bipyridine and its analogues with metal ions.

Dipole moment calculations of SF and ClO radicals have been carried out using the recently developed partial triples correction to Fock-space multi-reference coupled cluster method. Theoretical calculation of the doublet SF and ClO radicals is useful due to their importance in atmospheric chemistry. The dipole moments of these radicals are extremely sensitive to correlation effects. A brief insight to the way the triples correction has been implemented is presented. We compare the results obtained from our analytic response treatment with that of restricted open Hartree-Fock (ROHF) calculations. Results are presented for both relaxed and non-relaxed approach in the ROHF method. Results suggest the importance of triples corrections. The effects of orbital relaxation are also analysed from the results.

In this paper, we study the reactivity of diimines like 2, 2'-bipyridine, 1, l0-phenanthroline and 1, 2, 4-triazines using density-based reactivity descriptors. We discuss the enhancement or diminution in the reactivity of these ligands as a function of two substituent groups, namely methyl (-CH₃) group and phenyl (-C₆H₅) group. The global reactivity descriptors explain the global affinity and philicity of these ligands, whereas the local softness depicts the particular site selectivity. The inter-molecular reactivity trends for the same systems are analysed through the philicity and group philicity indices. The 𝜎-donor character of these ligands is quantified with the help of electron density profile. In addition, the possible strength of interaction of these ligands with metal ions is supported with actual reaction energies of Ru-L complexes.

The Z-vector method in the relativistic coupled-cluster framework is employed to calculate the parallel and perpendicular components of the magnetic hyperfine structure constant of a few small alkaline earth hydrides (BeH, MgH, and CaH) and fluorides (MgF and CaF). We have compared our Z-vector results with the values calculated by the extended coupled-cluster (ECC) method reported in Phys. Rev. A 91 022512 (2015). All these results are compared with the available experimental values. The Z-vector results are found to be in better agreement with the experimental values than those of the ECC values.