Møller-Plesset theory to second order for the study of molecuar systems in finite magnetic fields

London orbitals allows for non-perturbative treatment of magnetic fields. This can be used to explore how molecules behave in very strong finite magnetic fields, and also be used to probe complicated magnetic properties like hypermagnetizability without resorting to response theory. Classical MP2 and an atomic orbital based variant of MP2 with a Laplace transform ansatz were introduced to the London program, and successfully used to perform different quantum chemical calculations entailing magnetic fields of finite size