Systematic First-Principles Configuration-Interaction Calculations of Linear Optical Absorption Spectra in Silicon Hydrides: SiH ( = 1-3).

We have performed first-principles electron-correlated calculations employing large basis sets to optimize the geometries and to compute linear optical absorption spectra of various low-lying conformers of silicon hydrides: SiH, = 1, 2, 3. The geometry optimization for various isomers was carried out at the coupled-cluster singles-doubles-perturbative-triples [CCSD(T)] level of theory, while their excited states and absorption spectra were computed using a large-scale multireference singles-doubles configuration-interaction approach, which includes electron-correlation effects at a sophisticated level. Our calculated spectra are the first ones for SiH and SiH conformers, while for SiH, we obtain excellent agreement with the experimental measurements, suggesting that our computational approach is reliable.

Excited States and Optical Properties of Hydrogen-Passivated Rectangular Graphenes: A Computational Study.

In this paper, we perform large-scale electron-correlated calculations of optoelectronic properties of rectangular graphene-like polycyclic aromatic hydrocarbon molecules. Theoretical methodology employed in this work is based upon Pariser-Parr-Pople (PPP) π-electron model Hamiltonian, which includes long-range electron-electron interactions. Electron-correlation effects were incorporated using multi-reference singles-doubles configurationinteraction (MRSDCI) method, and the ground and excited state wave functions thus obtained were employed to calculate the linear optical absorption spectra of these molecules, within the electric-dipole approximation.