Relativistic effects, infrared intensities, diffusion and lithiation in InSb

We consider In4Sb4H18 cluster with zinc-blend structure of InSb. The cohesive energy and band gap of InSb were calculated by Unrestricted Hartree–Fock (UHF) and Density Functional Theory (DFT) method and it was shown that underestimated values of band gap can be decreased by considering the relativistic effects and in some cases InSb crystal even to be a semimetal. By calculating time-dependent DFT (TDDFT), the first three singlet and triplet excited energies were calculated and it was shown the 0.23 eV (band gap of InSb at 77 K) is placed between them. The infrared intensities were calculated and it is shown that the 367 cm−1 (294 cm−1 experimentally) mode can be attributed to the LO(Γ) in InSb. Finally it was shown that the Cadmium (Cd) diffuses substantially as CdIn and changes the first three singlet and triplet excited energies, but Lithium (Li) is placed in empty spaces of InSb crystal in the lithiation of InSb.