Semi‐ab initio tight‐binding band‐structure calculations of χ⁽³) (− 3ω; ω, ω, ω) in C, Si, Ge, SiC, BP, AIP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb

A full band‐structure calculation is made of the dispersion, anisotropy, and magnitude χ (3 ) for optical third harmonic generation (THG) in C, Si, Ge, SiC, BP, AIP, AlAs, AlSb, GaP, GaAs, GaSb, InP, InAs, and InSb. The calculation is performed using a semi‐ab initio tight‐binding band‐structure technique and standard perturbation theory within the random phase approximation and neglect of local field corrections. The sign of χ (3 ) (0) is positive for all materials, consistent with experimental results from the literature. Trends are investigated in the periodic table in the structure of χ (3 ), and shown that the structure in most materials is dominated by 3ω resonances with either the E 0 or E 1 optical peaks, with the E 2 critical points typically making a negligible contribution to χ (3 ).