The “invariance principle” in approximate molecular orbital theories

The widely used invariance “principle” of approximate MO theories is shown to be physically unreasonable and formally unnecessary. The use of ZDO-type schemes in an internally-defined orbital basis is proposed to replace this restrictive principle.     

Some comments on the counterpoise correction for the basis set superposition error at the correlated level

The use of the counterpoise method for the mitigation of basis set superposition error at the correlated level is discussed. Evidence is presented to show that the ghost basis plays a dual role in the counterpoise method: The orbitals of the system are improved by the ghost basis but at the expense of a nonphysical increase in the dimension of the virtual space. This second factor has no effect on application of the counterpoise method at the SCF level but it makes the use of the counterpoise method at the correlated level much less straightforward. © 1993 John Wiley & Sons, Inc.     

Optimal Batching in a Semi-Automated Order Picking System

As the materials handling revolution continues, the techniques of Management Science are finding more and varied application in the design and operation of production and distribution systems. This paper discusses the use of these techniques to batch orders in a semi-automated order-picking system of a Canadian provincial liquor board. The problem is formulated as a mixed-integer programming problem with the objective of arranging orders into batches so that the processing time is minimised. A sample problem is presented and solved, and computational aspects are discussed. Other possible application areas are outlined.     

Formation of fluoro-meisenheimer complexes using homogeneous and heterogeneous fluoride ion sources

1-Chloro-2,4-dinitrobenzene, 1-fluoro-2,4-dinitrobenzene and 1,3-dinitrobenzene form Meisenheimer complexes with tetra-n-butylammonium fluoride and alumina supported alkali metal fluorides. Both kinetically controlled and thermodynamically controlled complexes are observed.     

Surface effects on the Formation of Hydrogen Peroxide from dissociated water vapour

The formation of hydrogen peroxide at 77°K from water vapour dissociated in a low-pressure electrodeless discharge was investigated as function of the surface-to-volume ratio. S/V, of both coated and uncoated tubular reactors interposed between the discharge exit and the coolant level. As S/V was increased, the peroxide yield increased to a maximum value and then decreased; this maximum shifted to much lower values of S/V for KCl-coated and H₃PO₄-coated surfaces. Compared with uncoated Pyrex surfaces, H₃PO₄-coatings gave higher H₂0₂ yields whereas KCl-coatings gave lower yields. Surfaces coated well with ice did not show much effect, but condensed water films decreased the H₂O₂ yield. Similar results were obtained when the surface area and the volume traversed by the dissociated vapour were varied at constant S/V. These surface effects are discussed to show that the formation of H₂O₂ occurs via the cold surface reactions H + O₂ → O_aH and H + 0₂H → H₂O₂ and not by the dimerization of OH radicals.