Extension of the Time-Dependent Density Functional Complex Polarizability Algorithm to Circular Dichroism: Implementation and Applications to Ag8 and Au38(SC2H4C6H5)24

We detail the calculation of rotatory strengths as an extension of the complex polarizability algorithm of time dependent density functional theory (TDDFT) proposed in a recent publication (O. Baseggio, G. Fronzoni, M. Stener, J. Chem. Phys. 2015, 143, 024106). To demonstrate the generality and applicability of the proposed algorithm, we calculate the photoabsorption and circular dichroism (CD) spectra of Ag8 (as a validation case), Au38(SCH3)24 and Au38(SCH2CH2Ph)24 monolayer-protected gold clusters (as a system of great current interest for their optical properties). For Au38(SCH2CH2Ph)24, the computed CD spectrum agree well with the experimental data from the literature. Furthermore, a comparison of the calculated CD spectra of the two thiolate-protected nanoclusters reveals that the most distinctive features of the spectra are rather insensitive to the nature of the thiolate tail groups, which, however, play a significant role in shaping optical and dichroic response of the systems, especially in the higher-energy portion of the spectrum.