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Theoretical studies on the GenSim clusters have been carried out using advanced ab initio approaches. The lowest energy isomers were determined for the clusters with compositions n+m=2–5. All possible isomers arising due to permutations of Ge and Si atoms were investigated. The L-shaped structure for the trimers, tetragonal with diagonal bond for tetramers, and a trigonal bipyramid for pentamers represent the energy optimized ground state geometries. The bonding analyses revealed that the trimers and tetramers are stabilized through multicenter π bonding. In pentamers, this stabilizing factor is eliminated due to the further cluster growth. The ionization of clusters does not change their geometrical characteristics. The agreement of the calculated ionization and atomization energies with those obtained from the mass spectrometric studies (through estimated appearance potential) validated the reported structures of the clusters. The bonding properties of these species are discussed using their molecular orbital characteristics and analysis of natural bond orbital population data. [ABSTRACT FROM AUTHOR]

Theoretical studies on the electronic and thermodynamic properties of several electronic states of CeC2 and CeC2+ have been carried out employing state-of-the-art single- and multireference techniques. The ground and the low-lying electronic states of these two species have been found to possess C2v triangular structures. A 3B2 state has been found to be the ground state of CeC2 while for CeC2+ 2A2 is the ground state. The computed electron ionization energy is in excellent agreement with experiment. The experimentally observed thermodynamic properties (dissociation and atomization energies) of reactions involving CeC2 dissociation are corrected using the computed gas-phase properties of the molecule and the partition functions. The bent triplet and singlet state of CeC2 exhibit large dipole moments (7.0–10.5 D) and it is consistent with the ionic character (through dative charge transfer) of the cluster in ground and excited states. [ABSTRACT FROM AUTHOR]

Theoretical studies on the electronic and thermodynamic properties of several electronic states of CeC2 and CeC2+ have been carried out employing state-of-the-art single- and multireference techniques. The ground and the low-lying electronic states of these two species have been found to possess C2v triangular structures. A 3B2 state has been found to be the ground state of CeC2 while for CeC2+ 2A2 is the ground state. The computed electron ionization energy is in excellent agreement with experiment. The experimentally observed thermodynamic properties (dissociation and atomization energies) of reactions involving CeC2 dissociation are corrected using the computed gas-phase properties of the molecule and the partition functions. The bent triplet and singlet state of CeC2 exhibit large dipole moments (7.0–10.5 D) and it is consistent with the ionic character (through dative charge transfer) of the cluster in ground and excited states. [ABSTRACT FROM AUTHOR]

This work provides a comparison of neutral (H2O)2Arn and negatively charged (H2O)2-Arn complexes. The excess electron stabilizes the complexes and leads to the trans to cis rearrangement within the water dimer core. In the case of small complexes (n≤4) the microsolvation of the dimer by argon atoms arises on the trans side with respect to the donor water molecule. The stabilization of an excess electron is enhanced by the delocalization of the electronic charge density due to microsolvation. The process of cis to trans rotation is induced by the electric field of the approaching negative charge. The interaction energy decomposition suggests a more ionic character of binding in the negatively charged complexes. The attachment of an electron is controlled by the correlation energy. [ABSTRACT FROM AUTHOR]

Theoretical studies on the GenCm (n=1,2; m=1–3) microclusters have been performed using the state of the art calculations. Several alternative structures of these clusters were studied to locate the lowest-energy isomers. It is observed that the structures of the complexes result from the competition between ionic Ge–C, conjugated covalent C–C, and metallic Ge–Ge bonds. The ionization of the molecules enhances the ionic character of the Ge–C bond and has significant structural consequences. Using theoretically determined partition functions, thermodynamic data are computed and experimental enthalpies are enhanced. The ab initio atomization energies of germanium carbides compare well with corrected experimental functions. The experimental appearance potentials are well reproduced by the theoretical ionization potentials. [ABSTRACT FROM AUTHOR]

Electron localizability indicators based on the electron pair density ELI–D and ELIA Electron localizability indicators ELI-D and ELIA based on the electron pair density are studied for the correlated ground-state wavefunctions of N2, O2, F2, and Ne2 diatomics. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two indicators. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for O2 and F2, the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 [ABSTRACT FROM AUTHOR]

Electron localizability indicators based on the electron pair density ELI–D and ELIA Electron localizability indicators ELI-D and ELIA based on the electron pair density are studied for the correlated ground-state wavefunctions of N2, O2, F2, and Ne2 diatomics. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two indicators. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for O2 and F2, the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010 [ABSTRACT FROM AUTHOR]

Electron localizability indicators based on the parallel-spin electron pair density (ELI–D) and the antiparallel-spin electron pair density (ELIA) are studied for the correlated ground-state wavefunctions of Li2, Be2, B2, and C2 diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li2, B2, and C2 the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [ABSTRACT FROM AUTHOR]

Electron localizability indicators based on the parallel-spin electron pair density (ELI–D) and the antiparallel-spin electron pair density (ELIA) are studied for the correlated ground-state wavefunctions of Li2, Be2, B2, and C2 diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li2, B2, and C2 the reliable topology of ELI–D is obtained only at the correlated level of theory. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 [ABSTRACT FROM AUTHOR]

Electron localizability indicators based on the parallel-spin electron pair density (ELI-D) and the antiparallel-spin electron pair density (ELIA) are studied for the correlated ground-state wavefunctions of Li(2), Be(2), B(2), and C(2) diatomic molecules. Different basis sets and reference spaces are used for the multireference configuration interaction method following the complete active space calculations to investigate the local effect of electron correlation on the extent of electron localizability in position space determined by the two functionals. The results are complemented by calculations of effective bond order, vibrational frequency, and Laplacian of the electron density at the bond midpoint. It turns out that for Li(2), B(2), and C(2) the reliable topology of ELI-D is obtained only at the correlated level of theory., (Copyright 2009 Wiley Periodicals, Inc.)

Theoretical studies on the Ge n Si m clusters have been carried out using advanced ab initio approaches. The lowest energy isomers were determined for the clusters with compositions n+m=2-5. All possible isomers arising due to permutations of Ge and Si atoms were investigated. The L-shaped structure for the trimers, tetragonal with diagonal bond for tetramers, and a trigonal bipyramid for pentamers represent the energy optimized ground state geometries. The bonding analyses revealed that the trimers and tetramers are stabilized through multicenter pi bonding. In pentamers, this stabilizing factor is eliminated due to the further cluster growth. The ionization of clusters does not change their geometrical characteristics. The agreement of the calculated ionization and atomization energies with those obtained from the mass spectrometric studies (through estimated appearance potential) validated the reported structures of the clusters. The bonding properties of these species are discussed using their molecular orbital characteristics and analysis of natural bond orbital population data.