Theoretical study of Al(n) and Al(n)O (n = 2-10) clusters.
The stable structures, energies, and electronic properties of neutral, cationic, and anionic clusters of Al(n) (n = 2-10) are studied systematically at the B3LYP/6-311G(2d) level. We find that our optimized structures of Al5(+), Al9(+), Al9(-), Al10, Al10(+), and Al10(-) clusters are more stable than the corresponding ones proposed in previous literature reports. For the studied neutral aluminum clusters, our results show that the stability has an odd/even alternation phenomenon. We also find that the Al3, Al7, Al7(+), and Al7(-) structures are more stable than their neighbors according to their binding energies. For Al7(+) with a special stability, the nucleus-independent chemical shifts and resonance energies are calculated to evaluate its aromaticity. In addition, we present results on hardness, ionization potential, and electron detachment energy. On the basis of the stable structures of the neutral Al(n) (n = 2-10) clusters, the Al(n)O (n = 2-10) clusters are further investigated at the B3LYP/6-311G(2d), and the lowest-energy structures are searched. The structures show that oxygen tends to either be absorbed at the surface of the aluminum clusters or be inserted between Al atoms to form an Al(n-1)OAl motif, of which the Al(n-1) part retains the stable structure of pure aluminum clusters.
Evolution of the structural and electronic properties of beryllium-doped aluminum clusters: comparison with neutral and cationic aluminum clusters.
The lowest-energy structures of the Al(n)Be (n = 1-13) clusters are obtained and compared with the corresponding Al(n+1) and Al(n+1)(+) (n = 2-13) as well as Al(n)Mg clusters at the B3LYP/aug-cc-pVDZ level. The configurations of Al(n)Be show strong resemblances to those of pure Al(n+1) clusters, and the first three-dimensional ground state in the Al(n)Be clusters occurs for Al(3)Be. Various properties of the Al(n)Be clusters are systematically investigated using the CCSD(T) method and their thermodynamic properties are also compared with those of corresponding Al(n+1)(+) clusters. The evolution of the energetic and electronic properties with the size of the clusters shows the unique stability of the 20-valence electron systems Al(6)Be and Al(7)(+), which can be understood from the spherical jellium model (SJM). However, different from Al(7)(+) with 1s(2)1p(6)1d(10)2s(2) shell occupation, the electronic-shell structure of 1s(2)1p(6)1d(6)2s(2)1d(4) for the Al(6)Be cluster demonstrates that the impurity atom makes the molecular orbital distribution of doped clusters much more complex than that of pure metal clusters.
The relative sign of through-bond and through-space interactions; “sigma assistance” of cyclization and intramolecular hydrogen transfer
Abstract A perturbational frontier MO model indicates that the relative sign of the through-bond and through-space interaction in nonconjugated bifunctional molecules alternates with the number (N) of intervening sigma bonds. The qualitative predictions from the FMO model are in full accord with quantitative computational and experimental literature data, the latter being mainly available for N