FREQUENCY-DEPENDENT POLARIZABILITY AND HYPERPOLARIZABILITY OF NOVEL GERMANIUM-PHENYL NANOCLUSTER: A DFT INVESTIGATION

Njapba S. Augustine¹ and Galadanci M. S. Garba² 

ABSTRACT

DFT calculations of molecular structure parameters of [Ge₉(C₆H₅)] nanostructure in the gas phase were performed using the hybrid functional B3LYP with Lanl2dz basis sets. Also, TD-DFT calculations were performed to obtain the optical properties of the nanostructure. Different parameters of the optimized structure such as  the electronic properties, thermodynamic defects (i.e. vacancies and self-interstitial), dipole moment, mean polarizability, First-order hyperpolarizability and frequency-dependent first order hyperpolarizability of the energetically stable [Ge₉(C₆H₅)] nanostructure were calculated. The HOMO and LUMO energies are -6.229 eV and -3.563 eV respectively, with an energy band gap of 2.66 eV. The dipole moment of the nanostructure calculated was high about 7.7708 Debye. Nonlinear optical properties of the nanostructure were calculated at two levels of theory, B3LYP and CAM-B3LYP employing different frequencies. Theoretically calculated values of the static mean polarizability, anisotropic polarizability and First-order static hyperpolarizability were found to be esu, esu and esu respectively at B3LYP which are greater than the calculated values for CAM-B3LYP level. A similar trend is observed for the Frequency-dependent parameters, polarizability and First-order hyperpolarizability. The calculated First-order hyperpolarizability of the nanocluster material is greater than the value of the standard compound Urea ( esu). This result suggests germanium-phenyl  nanostructure is good as an optoelectronic device material.

Keywords: TD-DFT, Energy band gap, Polarizability, Hyperpolarizability,                            Defect, Nanocluster, Nonlinear.