In this study, we report a combined experimental and theoretical study on molecular structure and vibrational spectra of 3,5 di tert butyl 4 hydroxy benzoic acid. Molecular structure, vibrational, UV, NMR, HOMO-LUMO, MEP, NLO, NBO analysis of 3,5 di tert butyl 4 hydroxy benzoic acid The SHG of pure and doped TFP stones were examined through Nd:YAG Q-exchanged laser. Atomic electrostatic potential has been broken down the electronic properties such as excitation energies, oscillator quality, wavelengths and HOMO-LUMO energies were acquired by time-subordinate DFT (TD-DFT) approach. The HOMO-LUMO energies depict the charge exchange happens inside the particle. The steadiness and charge delocalization of the particle were likewise concentrations were done by characteristic security orbital (NBO) examination. The tentatively watched FT-IR and FT-Raman groups were allotted to various ordinary methods of the atom. FT-IR, UV-Vis, Thermal, Micro-hardness and Dielectric studies were additionally done for the pure and doped crystals. Powder X-beam diffraction studies were done and the cross section parameters were computed by minimum square technique in pure and doped crystals. In the present examination, a methodical study has been done on the development of unadulterated and Coumarin doped Tetrafluoro Phthalate precious stones. Spectroscopic, Homo-Lumo and NLO studies of tetra fluoro phthalate doped Coumarin crystals using DFT method Inclusion of the orbital energy calculated by PM7 as an additional descriptor significantly improved the quality of estimations (reducing the MAE in >30%). The impact of the quantum chemical calculation protocol was assessed with a subset of compounds. Random forest models predicted an external test set of 9989 compounds achieving mean absolute error (MAE) up to 0.15 and 0.16 eV for the HOMO and LUMO orbitals, respectively. Several machine learning algorithms were screened, and an applicability domain was defined based on Euclidean distances to the training set. The whole project involved the retrieval and generation of molecular structures, quantum chemical calculations for a database with >111 000 structures, development of new molecular descriptors, and training/validation of machine learning models. Machine learning algorithms were explored for the fast estimation of HOMO and LUMO orbital energies calculated by DFT B3LYP, on the basis of molecular descriptors exclusively based on connectivity. Pereira, Florbela Xiao, Kaixia Latino, Diogo A R S Wu, Chengcheng Zhang, Qingyou Aires-de-Sousa, Joao Machine Learning Methods to Predict Density Functional Theory B3LYP Energies of HOMO and LUMO Orbitals. Our approach may prove useful in characterizing organic photovoltaic devices in situ or even in operando Our model is used to predict the characteristic length scales of the flat P3TH polymer segments in P3HT and P3HT/PCBM blends before and after annealing. We propose a model connecting torsional disorder in a P3HT polymer to the HOMO-LUMO gap, which suggests that annealing helps to decrease the torsional disorder in the P3HT polymers. We find that annealing reduces the HOMO-LUMO gap of P3HT and P3HT/PCBM blends, whereas annealing has little effect on the HOMO-LUMO gap of PCBM. The electronic structure of -phenyl C 61 butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT), and P3HT/PCBM blends is studied using soft X-ray emission and absorption spectroscopy and density functional theory calculations. International Nuclear Information System (INIS) Linking the HOMO-LUMO gap to torsional disorder in P3HT/PCBM blends