Ab Initio Calculation and Theoretical Construction of the First Excitation Energy of Lithium Atom

Keywords: Variational ab initio methods, Slater-type orbitals (STO)

Abstract: This paper presents a variational ab initio approach to compute the first electronic excitation energy of the lithium atom from the ground state 1s²2s¹ to the excited state 1s²2p¹. We design a minimal Slater-type orbital (STO) basis set, implement exact one- and two-electron integrals from scratch in Julia using only standard libraries, and optimize the basis exponents variationally. The method employs a nonuniform radial grid for numerical integration and grid search for parameter optimization, yielding an excitation energy of 0.06748603 Hartree with optimized parameters $ζ1*$=2.680000, $ζ2*$=0.630000, $ζp*$=0.520000.

Submission Number: 252