Low-level DFT calculations II: molecules containing fluorine and second-row atoms

X alpha local spin density calculations were performed for a body of 112 mo lecules containing fluorine and second-row elements, silicon, phosphorus, s ulphur and chlorine. The parameter alpha was treated as a variable and adap ted to each molecule, depending upon the number and type of bonds involved. The X alpha atomization energies are in acceptable agreement with their ex perimental counterparts. The standard deviations, 5.6 and 6.2 kcal mol(-1) for the X alpha(6-31G**) and X alpha(3-21G) methods, respectively, compare well with those obtained earlier for molecules containing only first-row el ements. Compared to the sophisticated self-consistent hybrid B3LYP model, u sed here with a 6-311G(d,p) basis, our simplified approach permits consider able savings of computer time. It is shown that the 3-21G orbital basis gen erally offers a reasonable compromise between accuracy and economy. (C) 199 9 Elsevier Science B.V. All rights reserved.