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In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

Modern methods to compute them include Coupled cluster methods and Moller-Plasset perturbation theory, which includes correlation functions. John Poples work on them used primitive Gaussians as basis sets, and they are the eigenfunctions of the Fock operator in Hartree-Fock theory. Easily derived via the LCAO method, these entities are the solutions of the Schrodinger equation for a multi-body electronic Hamiltonian. They can be used to explain why dihydrogen can exist but dihelium cannot, and they come in bonding and antibonding varieties. FTP, name these regions of space around a molecule where electrons hang out.
Output:
Science