Quantum effects on the structure and energy of a protonated linear chain of hydrogen-bonded water molecules

Computer simulations of a protonated, linear cluster of four hydrogen-bonded water molecules, (O4H9)+, are reported. The potential energy surface governing the motion of the nuclei was described with the polarization model of Stillinger and co-workers. The quantization of all the hydrogen nuclei was treated with the discretized Feynman path integral formalism. Results indicate that quantum dispersion has a significant influence on the conformational fluctuations of the system at 300 K. Configurations in which the energy profile of the central proton along the transfer coordinate possesses a single- or double-well character occur spontaneously due to thermal fluctuations.