Is there an easy explanation of MP2 calculation [closed]








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for my master thesis I calculated some ring strains with MP2 calculation. It was not hard to calculate these things but I'm struggling to understand what the theory is about. Now I'm defending my work and I'm affraid that my professor asks questions about it.


So is there an "easy" way (not really easy but maybe without some hardcore quantum mechanics) to expain the MP2 calculation so an organic chemist can understand it?


Are there any good reasons to use MP2 instead of B3LYP or other DFT calculations? 
A friend in theoretical chemistry suggested MP2 but we never talked about why.


Thank you for your answers.


