Normal ordered exponential approach to thermal properties and time-correlation functions: general theory and simple examples

  title={Normal ordered exponential approach to thermal properties and time-correlation functions: general theory and simple examples},
  author={Marcel Nooijen and Song Bao},
  journal={Molecular Physics},
A normal ordered exponential parametrization is used to obtain equations for thermal one-and two-particle reduced density matrices, as well as free energies, partition functions and entropy for both Fermionic (electronic) and Bosonic (vibrational) Hamiltonians. A first principles derivation of the equations, relying only on a simple Wick’s theorem and starting from the differential equation dD̂ dβ = −(Ĥ − μN̂)D̂, is presented that yields a differential equation for the amplitudes representing… Expand

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