Effect of alkaline earth metal at the single wall CNT mouth on the electronic structure and second hyperpolarizability

Abstract

In the present work, electronic structure and second hyperpolarizability of a number of alkaline earth metals (M [Formula: see text] Be, Mg and Ca) complexes with carbon nanotube (CNT) has been studied by using different DFT functional. The complexes have sufficient thermal stability. Significant amount of charge transfer from metal to CNT results in stronger ground state polarization. The second hyperpolarizability obtained at different DFT functional (BHHLYP, CAM-B3LYP, B2PLYP, [Formula: see text]B97XD) showed a consistent trend. The magnitude of second hyperpolarizability of M@CNT[3,0] complexes enhances rather appreciably when a second metal atom is introduced into other mouth position. The longitudinal component of second hyperpolarizability of M@CNT[3,0]@M complexes increases with increasing size of metal atom. The magnitude of second hyperpolarizability of Ca@CNT[3,0]@Ca complex is comparable with Fe([Formula: see text]-C[Formula: see text]B[Formula: see text]. However, widening/lengthening of CNT markedly reduces the cubic responses. The two state model can qualitatively explain the variation of second hyperpolarizability.