Semi‐quantitative and semi‐empirical versions in the quasi‐relativistic SCF‐MO‐LCAO methods: Numerical calculations for (PtCl₆)²⁻

Abstract

AbstractsQuasi-relativistic (QR) versions of the CNDO and Mulliken-Wolfsberg-Helmholz (MWH) semiempirical methods based on the SCF-QR-MO-LCAO method given earlier are worked out. For the CNDO method only the basic formulas and matrix element expressions are given, while for the MWH one, the parametrization as well as the basis functions and group spinor overlap integral calculation were discussed. (PtC1,)'-complex was chosen for a test calculation. The energy level values and LCAO coefficients were obtained and compared with the nonrelativistic calculations. One of the results was the occurrence of a very strong reduction of the spin-orbit interaction due to covalency. The calculation proves the semi-empirical versions of the QR-MO-LCAO method to be quite realizable in practice.On prtsente des versions quasi-relativistes (QR) des mCthodes CNDO et de Mulliken-WolfsbergHelmholz (MWH), qui sont basCes sur une mtthode SCF-QR-MO-LCAO publiee anterieurement. Pour la mCthode CNDO on ne donne que les formules fondamentales et les expressions des ClCments de matrice, tandis que pour MWH on discute la paramktrisation ainsi que les fonctions de base et le calcul de I'inttgrale de recouvrement de groupe des spineurs. Un calcul du complexe (PtC16)'-a CtC choisi a titre d'exemple. Les niveaux d'knergie et les coefficients LCAO ont ttt obtenus et comparCs a ceux des calculs non-relativistes. II en rCsulte une forte rCduction de l'interaction spin-orbite due B la covalence. Le calcul dCmontre que les versions semiempiriques de la mtthode QR-MO-LCAO sont tout B fait praticables. Quasi-relativistische (QR) Versionen der CNDO-und Mulliken-Wolfsberg-Helmholz-(MWH)-Methoden werden vorgelegt. Diese basieren auf die fruher angegebene SCF-QR-Mo-LcAo-Methode. Fur die C"o-Methode werden nur die grundlegenden Formeln und die Matrixelementausdrucke gegeben, weil fur MWH sowohl die Parametrisierung als auch die Basisfunktionen und die Berechnung der Gruppeniiberlappungsintegrale der Spinoren diskutiert wird. Als Beispiel wurde eine Berechnung des Komplexes (PtC1,)'-gewahlt. Die Energiewerte und die LcAo-Koeffizienten wurden erhalten und mit denen der nichtrelativistischen Berechnungen verglichen. Es ergibt sich eine starke Reduktion der Spin-Bahn-Wechselwirkung, die der Kovalenz zugeschrieben werden kann. Die Berechnung zeigt, dass die halbempirischen Versionen der oR-Mo-LcAo-Methode auch praktisch ausfiihrbar sind.

Chemistry with ADF

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