Exploring molecular equilibria using quantum information measures

Abstract

The quantum information‐theoretic description of electron probabilities and currents in molecules is extended. The Harriman‐Zumbach‐Maschke framework of equidensity orbitals is reexamined and the nonclassical Fisher information contribution it generates is used to determine the system equilibrium states for the fixed (ground‐state) electron density/energy. The lowest of such variational “thermodynamic” states can in general exhibit the space‐dependent phase and hence also nonvanishing probability current. The phase/current feature of electronic states in Harriman's representation is emphasized throughout, the probability interpretation of its key constructs is given, and the phase shifts accompanying interactions between the equidensity orbitals are examined. The phase‐“temperature” concept is introduced as the information‐theoretic descriptor of probability currents in molecules and their fragments.