Département de chimie moléculaire

Linear-response time-dependent (TD) d.-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 GTO program deMon2k for the calcn. of electronic absorption spectra of N2 using the TD local d. approxn. (LDA). The two programs give comparable excitation energies and absorption spectra once suitably extensive basis sets are used. Convergence of LDA d. orbitals and orbital energies to the basis-set limit is significantly faster for BigDFT than for deMon2k. However the no. of virtual orbitals used in TD-DFT calcns. is a parameter in BigDFT, while all virtual orbitals are included in TD-DFT calcns. in deMon2k. As a reality check, we report the X-ray crystal structure and the measured and calcd. absorption spectrum (excitation energies and oscillator strengths) of the small org. mol. N-cyclohexyl-2-(4-methoxyphenyl)imidazo[1, 2-a]pyridin-3-amine. [on SciFinder(R)]