Dispersion of Linear and Nonlinear Optical Susceptibilities in Calcium Neodymium Oxyborate Ca4NdO(BO3)3-LDA versus GGA

We have performed ab inito theoretical calculations of the electronic structure and the linear and nonlinear optical susceptibilities for calcium neodymium oxyborate Ca4NdO(BO3)(3) using two approximations for the exchange correlation (XC) potentials, the local density approximation (LDA) and the generalized gradient approximation (GGA). Our calculations show that this compound is metallic-like, with density of states at the Fermi energy E-F, N(E-F), of 5.95 and 10.33 states/Ry-cell or bare electronic specific heat coefficients of 1.03 and 1.79 mJ/mol-K-2 for LDA and GGA, respectively. The overlap between the valence and conduction bands is strong, resulting in metallic behavior. We found that Nd-s/p/d, Ca-s/p. B-p, and O-s/p states controlled the overlapping around EF. The effect of LDA and GGA on the band structure, density of states, and linear optical properties is very small, while for the nonlinear optical properties, it is very pronounced. Our calculations show that chi((2))(111)(omega) is the dominant component for both LDA and GGA. We find opposite signs of the contributions of the 2 omega and 1 omega inter/intraband to the real and imaginary parts for the dominant component throughout the wide optical frequency range.