*Article* **Raman Spectroscopic Study of Five Typical Plasticizers Based on DFT and HF Theoretical Calculation**

**Tong Sun \*, Yitao Wang, Mingyue Li and Dong Hu**

College of Optical, Mechanical and Electrical Engineering, Zhejiang A&F University, Hangzhou 311300, China; 2020604021041@stu.zafu.edu.cn (Y.W.); lmy@stu.zafu.edu.cn (M.L.); 20180047@zafu.edu.cn (D.H.) **\*** Correspondence: suntong@zafu.edu.cn

**Abstract:** Phthalic acid esters (PAEs) are the most commonly used plasticizers, and long-term or high levels of exposure to PAEs have a huge potential risk to human health. In this study, the theories of Hartree–Fock (HF) and density functional theory (DFT) with different hybrid methods and basis sets were used to calculate the theoretical Raman spectra of five PAEs, and the comparison of calculated spectra between different theories, hybrid methods, and basis sets was conducted to determine the suitable theory with hybrid method and basis set for PAEs. Also, the Raman vibrations were assigned to the Raman peaks of PAEs according to the theoretical and experimental Raman spectra. The results indicate that DFT is more suitable for the theoretical study of PAEs than HF. In DFT, the hybrid method of B3LYP is more applicable to the theoretical study of PAEs than B3PW91, and the basis set of 6-311G(d, p) obtains the most consistent theoretical Raman spectra with the experimental spectra for PAEs. This study finds the optimal combination of the theoretical method and basis set for PAEs, and it will contribute to the establishment of the Raman fingerprint and the development of rapid detection for PAEs in the future.

**Keywords:** PAEs; Raman; DFT; HF; theoretical study
