In Figure , the IR spectra for isomers d, e, and f are illustrated, showcasing additional disparities between the HF and DFT methods. Specifically, the HF method failed to detect all functional groups in isomers d and f, missing key vibrational modes. For isomer e, HF managed to identify several vibrational frequencies, though it notably failed to capture the C-H stretch. In contrast, DFT, particularly when using the more advanced B3LYP-D3BJ functional and cc-pVDZ basis set, succeeded in identifying all the relevant functional groups and vibrational modes across these isomers. This not only highlights the adaptability and precision of the DFT approach but also underscores its comprehensive capability in detecting molecular properties with a higher degree of accuracy than HF. The improved performance of DFT, especially with the inclusion of dispersion corrections, makes it a more reliable method for complex molecular systems where the HF method may fall short. Figure focuses on the IR spectra of isomers g, h, and i, and offers an interesting contrast to earlier observations. In these cases, the HF method provided a more thorough analysis compared to its performance with earlier isomers, with several additional peaks detected at the expected frequencies. This improved performance, while notable, still fell short of capturing the C-H stretch, once again reflecting the method's limitations. On the other hand, the DFT method, using the B3LYP functional, successfully identified all the relevant vibrational modes and functional groups across these isomers. This consistent accuracy, particularly with regard to detecting the C-H and C-Cl stretching vibrations, reinforces the superiority of the DFT method in identifying molecular properties, even in cases where HF demonstrates some degree of success. The use of the B3LYP functional, which combines Hartree-Fock exchange with DFT, ensures a more precise calculation of electron interactions and molecular vibrations, making it the preferred method for studying the TCBD molecule.