Quantum Molecular Dynamics: Theory, methods, and applications

点击翻译按钮获取中文摘要

Our research is in the field of quantum molecular dynamics. One of the great challenges of theoretical chemistry is the study of quantum dynamics in systems containing a large number of atoms such as condensed phases, clusters, nano-structures and bio-molecules. We will develop simulation methods needed for the investigation of the behaviour of molecular species confined in superfluid environments, a fascinating state of matter. Recent progress in this area has allowed us to also consider the possibility of discovering new superfluids. Such studies require the inclusion of the internal structure (molecular rotations and vibrations) of hydrogen molecules in the theoretical formalism. We plan to develop computational algorithms based on the Feynman path integral formalism together with graphical Processing Unit (GPU) acceleration in order to perform these complex simulations. In a related area, new experiments on nano-confined molecules have recently revealed quantum many-body effects that yet remain to be explained. In particular, endohedral fullerenes where a guest molecule can be trapped inside a host nanocage provide a unique environment. We will study the case of H2O@C60 systems where a water molecule is trapped inside a C60 cage. We plan to develop novel path integral simulation techniques in order to calculate structural, energetic, and spectral properties of these nano confined water molecules. GPU acceleration will allow us to simulation a substantial number of such caged-water and probe the effects of many-body correlations of the properties of these quantum materials. Recent experiments on H2O@C60 crystals display an anomalous dielectric response and our simulation results will shed light on these unexplained results. The simulation technology developed in this work will also allow us to study the spin conversion process where a triplet ortho water can convert into a singlet para water molecule. We will further push the path integral framework and develop new approaches for quantum free energy calculations and quantum information. Free energy profiles are key in the description of chemical reactions and their quantum mechanical treatment remains a challenge for theoretical chemists. This challenge is due to the fact that a quantum mechanical treatment of atomic motion beyond the harmonic approximation requires great computational efforts. We will test these new ideas for hydrogen bonded systems such as water clusters. An important physical quantity at the core of quantum mechanical free energy profile is the diagonal reduced density matrix for the reaction coordinate. If one can access properties associate with the off-diagonal density matrix, new insight can be obtained via entanglement measures. We will develop new path integral algorithms for the calculation of the so-called Renyi entanglement entropy in order to further our knowledge of many-body correlations.