Clusters atomization energies

We see that the neutral fluorine atom has seven valence electrons that is, seven electrons occupy the outermost partially filled cluster of energy levels. This cluster of energy levels, the valence orbitals, contains one electron less than its capacity permits. Fluorine, then, has the capacity for sharing one electron with some other atom which has similar capacity. If, for example, another fluorine atom approaches, they might share... 

Stevens, G. F., and R. W. Wood, 1966, A Comparison between Burnout Data for 19 Rod Cluster Test Sections Cooled by Freon-12 at 155 psia and by Water at 1000 psia in Vertical Upflow, Rep. AEEW-R-468, UK Atomic Energy Authority, Winfrith, England. (5)... 

To improve on the CCSD description, we go to the next level of coupled-cluster theory, including corrections from triple excitations -see the third row of Table 1.4, where we have listed the triples corrections to the energies as obtained at the CCSD(T) level. The triples corrections to the molecular and atomic energies are almost two orders of magnitude smaller than the singles and doubles corrections. However, for the triples, there is less cancellation between the corrections to the molecule and its atoms than for the doubles. The total triples correction to the AE is therefore only one order of magnitude smaller than the singles and doubles corrections. 

Thermochemistry of cluster compounds. In this short summary of cluster structures and their bonding, a few remarks on their thermochemical behaviour are given, in view of a possible relationship with the intermetallic alloy properties. To this end we remember that for molecular compounds, as for several organic compounds, concepts such as bond energies and their relation to atomization energies and thermodynamic formation functions play an important role in the description of these compounds and their properties. A classical example is given by some binary hydrocarbon compounds. 

Noga, J., Valiron, P., Klopper, W. The accuracy of atomization energies from explicitly correlated coupled-cluster calculations. J. Chem. Phys. 2001, 115, 2022-32. 

Table 1 lists the atomization energies of the Na(3p)Arn clusters. The atomization energies found in the present work and those obtained by Tutein and Mayne are in very good agreement within 200 cm, whatever the cluster size. The size dependence of stabilities observed by Tutein and Mayne is confirmed. 

A final point concerns the comparison of the DDCI method and the CAS-SCF / CASPT2 approach. We have performed some test calculations for the step cluster using all electron basis sets ofmoderate size for all cluster atoms. These calculations not only permit a direct comparison of the two approaches for the inclusion of electron correlation but also provide a test of the ECP and basis used in the previously commented calculations Compared to the results listed in Table 2 for the surface, the DDCI excitation energies obtained with all electron basis sets change less than 0.1 eV for all states considered. Moreover. 

The chiral discrimination in the self-association of chiral l,3a,4,6a-tetrahydroi-midazo[4,5-d]imidazoles 3 has been studied using density functional theory methods [37], (Scheme 3.20). Clusters from dimers to heptamers have been considered. The heterochiral dimers (RR SS or SS RR) are more stable than the homochiral ones (RR RR or SS SS) with energy differences up to 17.5 kJ mol-1. Besides, in larger clusters, the presence of two adjacent homochiral molecules imposes an energetic penalty when compared to alternated chiral systems (RR SS RR SS...). The differences in interaction energy within the dimers of the different derivatives have been analyzed based on the atomic energy partition carried out within the AIM framework. The mechanism of proton transfer in the homo- and heterochiral dimers shows large transition-state barriers, except in those cases where a third additional molecule is involved in the transfer. The optical rotatory power of several clusters of the parent compound has been calculated and rationalized based on the number of homochiral interactions and the number of monomers of each enantiomer within the complexes. 

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