Structure and Stability of Endohedral Complexes X@(HAlNH)_(12) (X = He, Ne, Ar, Kr)

The structures of closo-hedral cluster (HAlNH)12 and endohedral complexes X@(HAlNH)12 (X = He, Ne, Ar, Kr) have been studied by using density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency, energetic parameters, magnetic shielding constants and nucleus independent chemical shifts (NICS) were discussed. The potential surface of guest X shifting from the cage center to a face of six- membered ring was calculated at the same level. The exit transition state was demonstrated with IRC calculations. It is found that X@(HAlNH)12 complexes are dynamically stable, and Ne@(HAlNH)12 is more energetically favorable than the other complexes in thermodynamics.

Encapsulation Chalcogen Anions in Perfluorinated Silicon Fullerene： X^2-@Si20F20 （X=O, S, Se）

The structures and stabilities of cage Si20F2o and its endohedral complexes X^2-@Si20F20 （X=O, S, Se） were determined at the B3LYP/6-31G（d） levels of density functional theory （DFT）. It is found that the adiabatic electron affinity （EAad） of host cage Si20F20 （1h） is higher than that of isolated O atom （4.24 vs. 1.46 eV）. This suggests the Si20F20 cage can selectively trap and stabilize the capsulated spherical anions. The calculations predict that X=S and Se are nearly located at the center of the cage, and O dramatically deviates from the center in C3v symmetry. Moreover, the corresponding X^2- @Si20F20 complexes have more negative inclusion energies （AEinc） and thermodynamic parameters （AZ） than X2 @C20F20. The amount of charge that is being transferred from the encapsulated anions to the cage increases with the atomic radius, i.e., from O^2- （ca. 45%）, S^2- （ca. 51%） to Se^2- （ca. 59%）, and such a novel model of cage may have practical uses as potential and electrical building units of nanoscale materials.

Structure and Stability of Endohedral Complexes X@（HBNH）12

Using quantum chemistry methods B3LYP/6-31＋＋G（d,p） to optimize endohedral complexes X@（HBNH）12 （X=Li^0/＋, Na^0/＋, K^0/＋, Be^0/2＋, Mg^0/2＋, Ca^0/2＋, H and He）, the geometries with the lowest energy were achieved. Inclusion energy, standard equilibrium constant, natural charge, spin density, ionization potentials, and HOMO-LUMO energy gap were also discussed. The calculation predicted that X=Na^0/＋, K^0/＋, Mg^0/2＋, Ca^0/2＋, H and He are nearly located at the center of （HBNH）12 cluster. Li^＋ lies in less than 0.021 nm departure from the center. Li and Be^0/2＋ dramatically deviate from the center. （HBNH）12 prefers to enclose Li^＋, Be^2＋, Mg^2＋, and Ca^2＋ in it than others. Moreover, M@（HBNH）12 （M=Li, Na, K） species are ＂superalkalis＂ in that they possess lower first ionization potentials than the Cs atom （3.9 eV）.

Anomalous Resistivity in Vanadium-Doped Semi-Insulating 4H-SiC Wafers

The resistivities of vanadium-doped semi-insulating 4H-SiC wafers were measured by a contactless resistivity measurement system. Anomalous resistivity was found in semi-insulating 4H-SiC wafer. Raman spectra of semi-insulating4H-SiC wafer indicated that the anomalous resistivity was caused by polytype inclusion. Based on the activation energies of different SiC polytypes calculated from resistivity versus temperature data measured by COREMA-VT, the resistivities in the vanadium-doped semi-insulating 4H-SiC wafer with 6H polytype inclusion were calculated. The calculated resistivities are quite consistent with the measured resistivities. Furthermore, the compensation mechanism for the formation of anomalous resistivity was proposed.