Ab initio study of the nonlinear optical properties of urea: Electron correlation and dispersion effects

Abstract

rnWe present the results of ab initio calculations on the first-, second-, and third-order molecular polarizabilities of urea. An efficacious general finite field perturbation approach, previously applied in the case of paranitroaniline, is extended to the evaluation of axial and nonaxial components of the nonlinear responses. The validity of our numerical procedure is examined at the Hartree-Fock level of theory by comparison with analytical derivative results. The impact of electron correlation is analyzed, by calculating the optical nonlinearities at the Moller-Plesset perturbation theory level. The second-order Moller-Plesset electron correlation correction is shown: (i) to enhance the third-order polarizability y by almost a factor of 2 and (ii) to include the major correlation effects as consideration of the fourth-order correction further improves the y components by less than 20%. We also discuss the frequency-dependence of the nonlinear optical properties of urea by presenting calculations of the dynamic components at the noncorrelated level of theory for different optical processes.

FT-IR, FT-Raman and ab-initio studies of 1,3-diphenyl thiourea

“…The calculated first hyperpolarizability of the title compound is 1.86x10 -30 esu, which is 14.36 times that of urea (0.13x10 -30 esu) [42]. The C-N distances in the calculated molecular structure vary from 1.3814 to 1.4188 Å which are intermediate between those of a C-N single bond (1.48 Å) and a C=N double bond (1.28 Å).…”

“…The C-N distances in the calculated molecular structure vary from 1.3814 to 1.4188 Å which are intermediate between those of a C-N single bond (1.48 Å) and a C=N double bond (1.28 Å). Therefore, the calculated data suggest an extended π-electron delocalization over the thiourea moiety [42,43] which is responsible for the nonlinearity of the molecule. We conclude that the title compound is an attractive molecule in future for non linear optical applications.…”

Computer simulation of the linear and nonlinear optical properties of liquid benzene: Its local fields, refractive index, and second nonlinear susceptibility

“…in steps of 0.001 a.u., and the property components are connected by a set of linear equations which are solved by a singular value decomposition method ͑SVD͒. 43 The molecular geometry used in the quantum calculations is as described in Ref. 44.…”

Vibrational spectroscopic (FT-IR, FT-Raman) and quantum chemical calculations of 1-(5,5-dioxido-10H-phenothiazin-10-yl)ethanone

“…The calculated first hyper polarizability of the title compound is 2.33 Â 10 À30 esu and which is 17.92 times that of the standard NLO material urea (0.13 Â 10 À30 esu) [71]. We conclude that the title compound is an attractive object for future studies of nonlinear optical properties.…”