Wavelet-based linear-response time-dependent density-functional theory

Abstract Linear-response time-dependent (TD) density-functional theory (DFT) has been implemented in the pseudopotential wavelet-based electronic structure program BigDFT and results are compared against those obtained with the all-electron Gaussian-type orbital program de M on 2 k for the calculation of electronic absorption spectra of N 2 using the TD local density approximation (LDA). The two programs give comparable excitation energies and absorption spectra once suitably extensive basis sets are used. Convergence of LDA density orbitals and orbital energies to the basis-set limit is significantly faster for BigDFT than for de M on 2 k . However the number of virtual orbitals used in TD-DFT calculations is a parameter in BigDFT , while all virtual orbitals are included in TD-DFT calculations in de M on 2 k . As a reality check, we report the X-ray crystal structure and the measured and calculated absorption spectrum (excitation energies and oscillator strengths) of the small organic molecule N -cyclohexyl-2-(4-methoxyphenyl)imidazo[1, 2- a ]pyridin-3-amine.