Hartree–Fock calculation of the electronic structure of a Cu+ impurity in NaCl

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Abstract
Hartree–Fock cluster calculations have been carried out for the ground 3d10 and excited 3d94s configurations of the Cu+ ion in a NaCl host. Special emphasis has been given to providing an accurate representation of the Coulomb potential due to the remainder of the lattice. Configuration coordinate curves were determined for the symmetric displacement of the nearest‐neighbor Cl− ions and are compared to recent Xα calculations. The Hartree–Fock equilibrium Cu–Cl distance was found to be 5.327 bohr, slightly shorter than the calculated nearest‐neighbor distance of 5.353 bohr for the pure NaCl host. Comparison of the Hartree–Fock and Xα ground and excited state energies, shows that the Xα approximation reverses the ordering of the 3T2g and 1Eg states, overestimates the equilibrium nearest‐neighbor distance, and predicts the a1g vibrational frequency to be about twice the Hartree–Fock value. Using the Franck–Condon factors found with the ab initio potential energy curves, the calculated bandwidths for the 1,3T2g states are found to be in excellent agreement with the low‐temperature absorption spectra.