The effective interactions of ions, dipoles and higher-order multipoles under periodic boundary conditions are calculated where the array of periodic replications forms an infinite sphere surrounded by a vacuum. Discrepancies between the results of different methods of calculation are resolved and some shape-dependent effects are discussed briefly. In a simulation under these periodic boundary conditions, the net Hamiltonian contains a positive term proportional to the square of the net dipole moment of the configuration. Surrounding the infinite sphere by a continuum of dielectric constant ε.' changes this positive term, the coefficient being zero as ε' ->∞ . We report on the simulation of a dense fluid of hard spheres with embedded point dipoles; simulations are made for different values of showing how the Kirkwood gr-factor and the long-range part of hA (r) depend on ε' in a finite simulation. We show how this dependence on ε' nonetheless leads to a dielectric constant for the system that is independent of ε . In particular, the Clausius-Mosotti and Kirkwood formulae for the dielectric constant e of the system give consistent ε values.

Amine catalysts can reduce the high temperatures and long exposure times required for SiO 2 atomic layer deposition ͑ALD͒ using SiCl 4 and H 2 O reactants. One problem is that the reaction product, HCl, readily reacts with the amine catalysts to form a salt. Salt formation can be avoided by using organometallic silicon precursors. This study investigated catalyzed SiO 2 ALD on BaTiO 3 and ZrO 2 particles using alternating exposures of tetraethoxysilane ͑TEOS͒ and H 2 O at 300 K with NH 3 as the catalyst. The sequential surface chemistry was monitored in a vacuum chamber using in situ transmission Fourier transform infrared ͑FTIR͒ spectroscopy. Alternating TEOS/NH 3 and H 2 O/NH 3 exposures yielded Si(OCH 2 CH 3 ) x * and SiOH* surface species, respectively, that sequentially deposited silicon and oxygen. Repetition of the TEOS and H 2 O exposures in an ABAB... reaction sequence led to the appearance of bulk SiO 2 vibrational modes. The infrared absorbance of these bulk SiO 2 vibrational modes increased with the number of AB reaction cycles. After SiO 2 deposition, the BaTiO 3 and ZrO 2 particles were examined using transmission electron microscopy ͑TEM͒. The TEM images revealed extremely uniform and conformal SiO 2 films. The measured SiO 2 film thicknesses were consistent with SiO 2 ALD growth rates of 0.7-0.8 Å per AB reaction cycle. The NH 3 catalysis mechanism was also explored by monitoring the FTIR spectra of hydroxylated SiO 2 particles vs. NH 3 pressure at constant temperature and vs. temperature at constant NH 3 pressure. The spectra revealed strong hydrogen bonding between NH 3 and SiOH* surface species that activates the oxygen in SiOH* for nucleophilic attack. Catalyzed SiO 2 at room temperature should be useful for deposition of inorganic and insulating films on thermally fragile organic, polymeric, or biological substrates.

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