Ab initio calculation of magnetic susceptibilities and screening constants using gauge invariant Gaussian orbitals

Abstract

The magnetic susceptibility and screening constant tensors are calculated using an ub initio finite perturbation SCF method, with gauge invariant Gaussian orbitals. The isoelectronic BH, BeH-, and CH+ molecules have been studied. The calculated values for BH are relatively different from those obtained by other methods. The CH+ molecule seems to exhibit a stronger temperature independent paramagnetism than BH, while the BeH-tnolecule would be diamagnetic. The screening constants of the heavy atom of thcse molecules prescnt a similar variation.The BH molecule seems to represent an interesting case of temperature independent paramagnetism. Its susceptibility and the screening constants of the H and B nuclei, have been calculated by various methods [ 1-51, The AIH molecule has also been studied, and its magnetic properties partly prescnt some analogy with those of BH [ 6 ] .It seemed interesting to us to treat other molecules isoelectronic of BH like BeHand C H + in order to study them when this phenomenon occurs.Finite perturbation SCF method with gauge invariant contracted Gaussian orbitals (GIGO) [3,7] has been used throughout this work. The calculated susceptibilities and screening constants are then strictly gauge invariant.The calculations have been carried out using Huzinaga-type [XI double 7eta splitvalence contracted Gaussian basis sets [ 3 s 2 p ] for the heavy atom, and [ 2 s ] for hydrogen, corrected with gauge factors. The three molecules under consideration, were treated with fixed interatmic distances of 2.500, 2.329, and 2.1 37 a.u., respectively, for BeH-, BH, and CH+.In Table I, we compare the values of the magnetic susceptibilities of BH calculated by different methods.