Free online resources for molecular modeling and computational chemistry

[ModestyKing]

Hi there!
Is there an online, hopefully free resource (preferably textbook) that details the process of molecular modeling? Specifically, computationally performing geometry optimizations, vibrational analyses, calculating Raman spectra, detailing the theory behind Hartree-Fock, DFT, post-HF methods, etc? I borrowed "Introduction to Molecular Modeling" by Jan Jensen from a postdoc here (excellent book, looking for something like that), but couldn't keep it forever, and I'd like to have an online resource anyway, easy access.

Two other smaller requests: A resource detailing the Raman active modes of hydrocarbons (polycyclic aromatic molecules, chain molecules, and others like stearic acid) would be great, as well as a resource that puts the theory behind DFT in simple terms (I haven't taken QM yet but I really should understand what I'm doing research on xD)

Thanks!

 

[ModestyKing]

I can try!
I'm new to Raman Spectroscopy. I'm doing research into PAHs (polycyclic aromatic hydrocarbons), using computational software/methods. I'm new to the field, and not knowledgeable enough to read the papers around. Are there resources I can find to get started in a holistic way? Textbook, video series, etc.