Quantum Molecular Dynamics: Theory, methods, and applications

我们的研究方向是量子分子动力学。理论化学面临的巨大挑战之一是研究包含大量原子的系统中的量子动力学，如凝聚态相、簇、纳米结构和生物分子。***我们将开发用于研究被限制在超流体环境（一种迷人的物质状态）中的分子物种行为所需的模拟方法。这一领域的最新进展使我们能够考虑发现新的超流体的可能性。这类研究需要在理论形式体系中包含氢分子的内部结构（分子旋转和振动）。我们计划开发基于费曼路径积分形式和图形处理单元（GPU）加速的计算算法，以执行这些复杂的模拟。在一个相关领域，对纳米受限分子的新实验最近揭示了仍有待解释的量子多体效应。特别是，内嵌富勒烯，客人分子可以被困在宿主纳米笼中，提供了一个独特的环境。我们将研究H2O@C60系统的情况，其中水分子被困在C60笼中。我们计划开发新的路径积分模拟技术，以计算这些纳米密闭水分子的结构、能量和光谱特性。GPU加速将允许我们模拟大量这样的笼水，并探测这些量子材料属性的多体相关性的影响。最近对H2O@C60晶体的实验显示出异常的介电响应，我们的模拟结果将揭示这些无法解释的结果。在这项工作中开发的模拟技术也将使我们能够研究自旋转换过程，其中三重态正交水可以转化为单线态对位水分子。我们将进一步推进路径积分框架，开发量子自由能计算和量子信息的新方法。自由能谱是描述化学反应的关键，其量子力学处理仍然是理论化学家面临的一个挑战。这一挑战是由于一个事实，量子力学处理原子运动超越调和近似需要大量的计算工作。我们将在氢键系统（如水簇）中测试这些新想法。在量子力学自由能谱中，一个重要的物理量是反应坐标的对角化密度矩阵。如果可以访问与非对角线密度矩阵相关的属性，则可以通过纠缠度量获得新的见解。我们将开发新的路径积分算法来计算所谓的Renyi纠缠熵，以进一步了解多体关联

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.**