CALCULATION OF THE PRESSURE SHIFTS OF THE QUARTET STATES OF RUBY

Hartree-Fock and configuration interaction calculations have been carried out on the lowest quartet states of ruby (Al2O3:Cr3+) using a cluster approximation for the crystal in order to determine the shifts of their relative energies with increasing pressure. The accuracy of the cluster was tested by calculating the equilibrium positions of Al3+ and Cr3+ with respect to displacement along the c axis and comparing to experiment. The predicted pressure-induced shifts of the 4E(T2g), 4A(T2g), 4E(Ta1g), and 4A(Ta1g) states are compared to measurements of Stephens and Drickamer (J. Chem. Phys. 1961, 35, 427) and are in good agreement at pressures below 10 GPa. © 1990 American Chemical Society.