Hyperpolarizabilities of one-dimensional Hn systems: Second hyperpolarizability density analyses for regular and charged solitonlike linear chains

Ž . ABSTRACT: Ab initio calculations of the second hyperpolarizabilities g for oneŽ . dimensional hydrogen chains H with different bond-length alternations and charges n are performed. We investigate their signs, magnitudes, and chain-length dependences at various electron correlation levels using an extended basis set. Remarkable differences in the g are observed for different bond-length alternations and for different charged states. In order to elucidate the differences in g , spatial contributions of electrons to the g are analyzed for these short and long H chains by using the second hyperpolarizability n density plots. The effects of the introduction of charged defects into the linear chains on the g are also investigated by varying the intercharged defects distance. Q 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 269]282, 1998