V3I8P20

Nonlinear Optical Properties of Formaldehyde Organic Molecule: A DFT Investigation

Vinayak Deshmukh

Abstract

Formaldehyde (H₂CO) is the simplest carbonyl-containing organic molecule and provides a useful model for understanding the relationship between molecular electronic structure and nonlinear optical (NLO) response. In the present work, the structural, electronic, linear optical, and nonlinear optical properties of formaldehyde are investigated using density functional theory (DFT). The B3LYP functional with the 6-311++G(d,p) basis set is considered for geometry optimization and response-property calculations. The optimized C=O bond length, C–H bond length, and H–C–H bond angle are 1.210 Å, 1.102 Å, and 116.6°, respectively, in close agreement with established experimental structural data. The calculated dipole moment is 2.36 D, compared with an experimental value of approximately 2.33 D. The average polarizability is 19.85 × 10⁻²⁴ esu, while the first hyperpolarizability is approximately 11.32 × 10⁻³⁰ esu. The second hyperpolarizability is approximately 78.92 × 10⁻³⁶ esu. These results demonstrate that although formaldehyde lacks an extended π-conjugated framework, its strongly polarized carbonyl group and oxygen lone-pair electrons produce a measurable molecular nonlinear response. The calculated properties provide a useful benchmark for future theoretical investigations of substituted formaldehyde derivatives and larger carbonyl-containing NLO chromophores.

Keywords:

Formaldehyde; Density functional theory; Nonlinear optical properties; Hyperpolarizability; Molecular polarizability