Jellium-model calculation for monomer and dimer decays of some potassium clusters

We have studied several decay processes of potassium clusters and found that a dimer-decay mechanism can explain the observed lowest abundance of K₁₀ in the K _n mass spectra. Total-energy curves for decay processes are calculated using a jellium-background model for positive-ion cores and the local-spin-density-functional approximation for valence electrons. The energy-barrier height for a dimer decay of K₁₀ from the energy-minimum point is found to be 0.18 eV, which is a reasonable magnitude for the decay to take place thermally in the experiment. The monomer decay of K₉ and the dimer decay of K₁₁, which are expected to be the most favorable decays of K₉ and K₁₁, are found to have high barriers. Monomer and dimer decays of K₈ are also studied and the monomer decay is found to be more favorable, in accord with the high-nozzle-temperature mass spectrum.     

Structure of the Si(111)−2 × 1 surface with 13 ML Ge coverage

Two different $\text{3}\text{×}\text{3}\text{R30°}$ adatom models for $\text{1}\text{3}$ monolayer Ge coverage of the Si(111)?2 × 1 surface were studied with the Pseudopotential method. Total energy calculations indicate that the T₄ model (adatom above the second layer) is preferable to the H₃ model (adatom above the hollow site)     

The formation and molecular structure of acetylcyclopentadienylsodium-tetrahydrofuranate

Acetylcyclopentadienylsodium has been isolated in crystalline form as a THF adduct from a reaction between cyclopentadienylsodium and methyl acetate in THF solution. The product has been characterized by means of a single-crystal X-ray diffraction study. {[C₅H₄CMeO]Na·THF}_n crystallizes in the monoclinic space group P2₁/c with unit cell parameters a 6.698(3), b 16.095(4), c 10.661(3) Å, β 92.93(3)° and D_c 1.17 g cm^?3 for Z = 4. Least-squares refinement led to a final R value of 0.080 based on 661 independent observed reflections. The coordination sphere around each sodium atom consists of the oxygen atoms from two C₅H₄CMeO ligands, the oxygen atom of the THF molecule, and an ion contact pair between the sodium and the five ring carbon atoms of the C₅H₄CMeO ligand.     

Oxindoles from α-acyloxyamides

Oxindoies have been obtained in good yields from the reaction of several a-acyloxy-α,α-diphenylacetanilides and boron trifluoride etherate. The reaction probably occurs by hydrolysis of the ester followed by electrophilic substitution of the resultant carbonium ion on the anilide ring.     

Pressure coefficients of band gaps in semiconductors

A first principles pseudopotential method within the local density approximation is used to calculate the pressure coefficients for band gaps in several diamond and zincblende semiconductors. Despite the underestimation of the band gaps found in almost all local density calculations, the predictions for the linear pressure coefficients and the critical pressures for conduction band inversion are consistent with experiment for all cases considered.