Calculation of excitation energies using locally-projected real-space geminal screened electron-hole interaction kernel

The geminal-screened electron-hole interaction kernel (GSIK) is a real-space representation for describing electron-hole correlation in charge-neutral excitations. Unlike MBPT and EOM methods, the GSIK method avoids using virtual or unoccupied orbitals for constructing electron-hole interaction kernel. This feature allows GSIK method to be used for chemical systems where inclusion of a large number of unoccupied orbitals will be computationally prohibitive. This talk will present the locally-projected formulation of the GSIK method where the electron-hole interaction kernel is calculated using an atom-in-cluster approach. It will be demonstrated that the local-projection allows the evaluation of the kernel to be performed at a linear-scaling cost. The locally-projected GISK method was applied to large metallic (Au₃₀₀) and semiconductor (Pb₁₅₀S₁₅₀) nanocluster for calculation of optical gap and electron-hole binding energies. The results from these calculations demonstrate the efficacy of the GSIK method for capturing electron-hole correlation in large clusters and nanoparticles.