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This article presents an assessment of methods to study the second harmonic generation (SHG) response of organic molecular crystal. We incorporated the discrete solvent reaction field model, density functional theory, and the local field approximation (designated as the LF-DRF/DFT) to investigate the SHG susceptibilities of the chromophore of 2-carboxylic acid-4-nitropyridine-1-oxide (POA). In experiment, the POA appears in two different polymorphic crystal structures easily identified by noticeable differences in the melting points and SHG susceptibilities. In this work, we tried to utilize the LF-DRF/DFT in a supermolecular framework to differentiate the two crystals. While focusing on the ratio of the calculated SHG susceptibilities for the two crystals, at optical wavelength of 1064 nm, the S12 g and SSB-D exchange–correlation functionals within a 5 × 5 × 5 extended architecture produced 2.16 and 2.08, differing from the experimental estimate of 2.16 by 0 and 3.7 %, respectively.

We have assessed six range-separated hybrids (CAM-B3LYP, LC-PBE, ωB97, ωB97X, ωB97X-D and M11) in evaluating the dynamic quadratic polarizability along the direction of the molecular dipole moment, β μ (−2ν; ν; ν; 0), by comparing with MP2(Full)-calculated data. There are 104 solution-phase organic molecules included in the set. Both geometry optimizations and β μ (−2ν; ν; ν; 0) computations have been carried out by the same functional. Calculated results showed that simultaneous modeling geometrical and electronic effects improved significantly the nonlinear optical (NLO) property of interest. More generally, our numerical assessment revealed that the CAM-B3LYP functional could be the reasonable choice for NLO property computations.

The dynamic second-order hyperpolarizability from the third-harmonic generation experiment, 〈γ〉(−3ω;ω;ω;ω), of 59 solution-phase organic molecules has been theoretically calculated and compared with available experimental data. The DFT/6-311+G(2d,p)//(CAM-)B3LYP/6-31G(2df,p) level of theory with the polarizable continuum model was employed to evaluate the static second-order hyperpolarizability. The theoretical static values were then corrected to dynamic estimates of 〈γ〉(−3ω;ω;ω;ω) by employing a two-level approximation (Chen et al. in J Chem Phys 101(7):5860–5864, 1994). Calculated results showed that for the property of interest, the range-separated hybrids provided more accurate and consistent estimate than the global hybrids and the CAM-B3LYP optimized geometry delivered more accurate estimate than the B3LYP optimized geometry.

The conventional method for determining ergot alkaloids in fermentation media is laborious and time consuming, largely because of the chloroform extraction procedure employed. A new and simplified method, without chloroform extraction, for measuring alkaloid in culture liquid and in colonies has been developed. The details of the procedure and its application are described. Estimates of alkaloid by the new method were about 6% higher than by the conventional method. The advantages of the new method are that it is accurate, rapid, safe and versatile in use, especially in the large scale screening of strains of the ergot fungus.