STRUCTURE, ENERGETICS, AND THERMODYNAMICS OF HYDROGEN BONDED MOLECULAR CLUSTERS

从分子团簇的结构、能量和热力学性质的研究中，我们可以了解到生物系统中氢键相互作用的重要性。由于在聚类研究中遇到的实验困难，计算机模拟已经成为理论描述这类系统的有力工具。在此基础上，我们提出用模拟退火方法研究几种氢键分子团簇的结构和能量学。在表征了这些团簇的势能面之后，将使用经典和量子蒙特卡罗技术获得热力学性质。与蒙特卡罗方法不同，量子蒙特卡罗方法是完全量子力学的，因此振动自由度、非调和性和隧道效应将同时得到正确和严格的处理。本研究将严格包括量子效应在分子团簇的热力学性质描述与现实的粒子间势。同时，它将解决计算机模拟的几个重要方面，如组态空间的适当采样和量子热力学系综平均的收敛性。选择要考虑的分子簇是因为它们在大分子系统的生物活性区域中的重要性。因此，理论描述将有助于理解大分子系统特定区域的分子间相互作用。

Much can be learned about the importance of hydrogen bond interactions in biological systems from studies related to the structure, energetic and thermodynamic properties of molecular clusters. Owing to the experimental difficulties encountered in cluster studies, computer simulations have emerged as a powerful tool in the theoretical description of such systems. Based on this, we propose to study the structure and energetics of several hydrogen bonded molecular clusters by means of simulated annealing procedures. After characterizing the potential energy surface for these clusters, thermodynamic properties will be obtained using both Classical and Quantum Monte Carlo techniques. Unlike Monte Carlo methods, the Quantum Monte Carlo approach is fully quantum mechanical so that the vibrational degrees of freedom, anharmonicities and tunneling effects will be correctly and rigorously treated simultaneously. This study will rigorously include quantum effects in the thermodynamic properties of molecular clusters described with realistic inter-particle potentials. At the same time, it will address several important aspect of computer simulations such as proper sampling of configuration space and convergence of quantum thermodynamic ensemble averages. The molecular clusters to be considered have been chosen because of their importance in biologically active regions of macromolecular systems. Hence, the theoretical description will contribute to the understanding of intermolecular interactions in the specific regions of macromolecular systems.