Magnetically induced current densities in Al42- and Al44- species studied at the coupled-cluster level -: art. no. 214308

Magnetically induced current densities in the four-membered rings of Al-4(2-) and Al-4(4-) species have been calculated at the coupled-cluster singles and doubles (CCSD) level by applying the recently developed gauge-including magnetically induced current (GIMIC) method. The strength of the ring-current susceptibilities were obtained by numerical integration of the current densities passing through a cross section perpendicular to the Al-4 ring. The GIMIC calculations support the earlier notion that Al-4(2-) with formally two p electrons sustains a net diatropic ring current. The diatropic contribution to the ring-current susceptibility is carried by the electrons in both the sigma (16.7 nA/T) and the pi (11.3 nA/T) orbitals. The induced ring current in the Al-4(4-) compounds, with four p electrons, consists of about equally strong diatropic sigma and paratropic pi currents of about 14 and - 17 nA/T, respectively. The net current susceptibilities obtained for Al4Li-, Al4Li2, Al4Li3-, and Al4Li4 at the CCSD level using a triple-zeta basis set augmented with polarization functions are 28.1, 28.1, -5.9, and -3.1 nA/T, respectively. The corresponding diatropic (paratropic) contributions to the ring-current susceptibilities are 32.4 (0.0), 36.7 (0.0), 18.9 (-19.9), and 18.6 (-16.8) nA/T, respectively. For the Al-4(2-) and Al-4(4-) species, the net currents circling each Li+ cation is estimated to 4.3 and 2.4 nA/T, respectively. (c) 2005 American Institute of Physics.