Benchmark study of the linear and nonlinear optical polarizabilities in proto-type NLO molecule of para-nitroaniline.

In the present investigation, for the first time, we have performed a thorough study about different functionals and basis sets for linear and nonlinear optical (NLO) properties of para-nitroaniline (p -NA), which is considered as proto-type NLO molecule, among organic NLO materials. There is a dire need of such data base for p -NA because many investigators are using such values of p -NA for comparative analysis. A range of different functionals including HF, BLYP, PW91, PBE, B3LYP, M06, M06-2X, PBE0, BHandHLYP, CAM-B3LYP, LC-BLYP, and B3LYP-D3 are applied in conjugation with several commonly basis sets such as 6-31G*, 6-311G*, 6-311G**, 6-311+G**, cc-pVDZ, and cc-pVTZ. A variety of functional and basis sets combinations are calculated and graphically compared with each other. The calculated total dipole moment for the p -NA is found to be 6.79 D which is quite closer to experimentally determined value. The lowest calculated value for linear isotropic polarizability at HF/6-31G* level of theory is 1 1. 7 4 × 1 0 − 2 4 esu while higher values observed with remaining all methods especially 14% polarizability increases in presence of basis set with diffuse functions and similar trend of variation is also observed in linear anisotropic polarizability. Similarly, the calculated value of frequency dependent second-order polarizability is found to be 9. 5 9 × 1 0 − 3 0 esu at PBE0/6-311+G** level of theory which is quite closer to experimental value of 9. 6 × 1 0 − 3 0 esu. A comparison between the calculated and experimental results shows good agreement among geometries, dipole moments and NLO polarizabilities for p -NA. Moreover, the frontier molecular orbital (FMO) and electron density difference map (EDDM) analysis along with density of state (DOS) plots are also presented to get more physical intuitions into the structure–property relationship and electronic communications between terminal accepter and donor groups through π -conjugation. The present investigation provides benchmark data including various commonly used functionals and basis sets for the calculation of NLO properties of p -NA. Thus, the present investigation will put straight several future studies when it comes to comparative NLO study of organic materials. • The present investigation provides benchmark data including various commonly used functionals and basis sets for the calculation of NLO properties of para-nitroaniline. • Additionally, we explore the electronic communications between terminal accepter and donor groups through π-conjugation in p-NA. [ABSTRACT FROM AUTHOR]