Results on structural, energetic, electronic, and magnetic properties of linear sandwich VnBzn+1 clusters obtained using high-accuracy density functional computations are presented and analyzed. Energetically close-lying configurations and states of different spin-multiplicities are identified. The computed characteristics are in good agreement with the available experimental data. The computations predict that the most stable forms of the clusters in the size range n >/= 4 are chiral. This feature, combined with the magnetism of these systems, makes them of potential importance as building blocks of nanosystems with coupled optical and magnetic functionalities.

Structural and electronic properties of neutral and anionic magnesium clusters with 2 to 22 atoms are studied using gradient-corrected density functional theory. A new scheme for the conversion of the Kohn−Sham eigenenergies into electron binding energies is utilized to compute the difference in the binding energies of the two most external electrons in the anionic clusters. The results are in very good agreement with the data obtained in recent electron photodetachment experiments. The other electronic properties studied include (a) the binding energy, the second difference of the total energies, the HOMO−LUMO gap, and the vertical ionization potential of the neutral clusters; (b) the vertical electron detachment energy of the anionic clusters; and (c) the character of bonding in both the neutral and the anionic clusters. The analysis focuses on the finite-size analogue of the insulator-to-metal transition. The role and manifestation of the finite-size effects are discussed, and some important implications regarding the interpretation of the experimental data are pointed out.

Diffusion Monte Carlo computations, with and without importance sampling, of the zero-point properties of H(5)(+) and its isotopomers using a recent high accuracy global potential energy surface are presented. The global minimum of the potential possesses C(2v) symmetry, but the calculations predict a D(2d) geometry for zero-point averaged structure of H(5)(+) with one H atom "in the middle" between two HH diatoms. The predicted zero-point geometries of the deuterated forms have H in the middle preferred over D in the middle and for a nonsymmetric arrangement of D atoms the preferred arrangement is one which maximizes the number of D as the triatomic ion. We speculate on the consequences of these preferences in scattering of H(2)+H(3)(+) and isotopomers at low energies, such as those in the interstellar medium.

A back-propagation neural network is utilized to fit the potential energy surfaces of the H3+ ion, using the ab initio data points of Dykstra and Swope, and the Meyer, Botschwina, and Burton ab initio data points. We used the standard back-propagation formulation and have also proposed a symmetric formulation to account for the symmetry of the H3+ molecule. To test the quality of the fits we computed the vibrational levels using the correlation function quantum Monte Carlo method. We have compared our results with the available experimental results and with results obtained using other potential energy surfaces. The vibrational levels are in very good agreement with the experiment and the back-propagation fitting is of the same quality of the available potential energy surfaces.

The binding energies of the two most external electrons in Mg- n, n=2-22, clusters are computed using the gradient-corrected density functional theory and a new scheme for converting the Kohn-Sham eigenenergies into electron removal energies. The computations are performed for the anionic clusters considered in the most stable configurations of both Mg- n and Mg n. The results are compared with photoelectron spectroscopy data [O. C. Thomas, following Letter, Phys. Rev. Lett. 89, 213403 (2002)]], and their implications for the finite-size analog of the nonmetal-to-metal transition are analyzed.