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Linus Pauling contributions span structural biology, chemistry in its broadest definition, quantum mechanical theory, valence bond theory, and even nuclear physics. A principal tool developed and used by Pauling is Xray, and electron, diffraction. One possible extension of the Pauling oeuvre could be the marriage of crystallography and quantum mechanics. Such an effort dates back to the sixties and has now flourished into an entire subfield termed quantum crystallography. Quantum crystallography could be achieved through the application of Clinton equations to yield N-representable density matrices consistent with experimental data. The implementation of the Clinton equations is qualitatively different for small and for large systems. For a small system, quantum mechanics is extracted from Xray data while for a large system, the quantum mechanics is injected into the system. In both cases, Nrepresentability is imposed by the use of the Clinton equations., 20 pages, 3 figures

Consider a projector matrix P, representing the first order reduced density matrix in a basis of orthonormal atom-centric basis functions. A mathematical question arises, and that is, how to break P into its natural component kernel projector matrices, while preserving N-representability of P. The answer relies upon 2- projector triple products, P'jPP'j. The triple product solutions, applicable within the quantum crystallography of large molecules, are determined by a new form of the Clinton equations, which - in their original form - have long been used to ensure N-representability of density matrices consistent with X-ray diffraction scattering factors.

The sources behind numerous key diffuse interstellar bands (DIBs) remain elusive, and thus evidence is presented here that a family of seven anionic hydrogen atomic clusters (H(-)2n+1, n = 1 to 7) are pertinent contributors. Configuration interaction calculations show hat these charge-induced dipole clusters are stable at temperatures characteristic of the interstellar medium, and emerge from the most abundant element in the Universe. The clusters' spectra yield 25 absorption optical lines that align with observed DIBs to within the computational uncertainties. The absorption bands are due to excitations from the ground states of the clusters to metastable states., Comment: 20 pages in total including 3 figures, 3 tables, and Supporting Information