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Finite-Temperature Correlation Functions Obtained from Combined Real- and Imaginary-Time Propagation of Variational
Jens Aage Poulsen1, Gunnar Nyman1
1Department of Chemistry and Molecular Biology, University of Gothenburg, SE 413 90 Gothenburg, Sweden.
Abstract:
We apply the so-called variational Gaussian wavepacket approximation (VGA) for conducting both real- and imaginary-time dynamics to calculate thermal correlation functions. By considering strongly anharmonic systems, such as a quartic potential and a double-well potential at high and low temperatures, it is shown that this method is partially able to account for tunneling. This is contrary to other popular many-body methods, such as ring polymer molecular dynamics and the classical Wigner method, which fail in this respect. It is a historical peculiarity that no one has considered the VGA method for representing both the Boltzmann operator and the real-time propagation. This method should be well suited for molecular systems containing many atoms.
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