High-accuracy ab-initio quantum chemistry by means of an SU(2) x U(1) invariant matrix product state Ansatz: the static second hyperpolarizability
Abstract
We have implemented the single-site density matrix renormalization group algorithm for the variational optimization of SU(2) × U(1) (spin and particle number) invariant matrix product states for general spin and particle number symmetric fermionic Hamiltonians. This class also includes non-relativistic quantum chemical systems within the Born-Oppenheimer approximation. High-accuracy ab-initio finite field results of the longitudinal static polarizabilities and second hyperpolarizabilities of one-dimensional hydrogen chains are obtained with the algorithm. A comparison with other methods is made.
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