STRUCTURE, ENERGETICS, AND THERMODYNAMICS OF HYDROGEN BONDED MOLECULAR CLUSTERS

通过对分子团簇的结构、能量和热力学性质的研究，可以了解到氢键相互作用在生物系统中的重要性。由于在集群研究中遇到的实验困难，计算机模拟已经成为对这类系统进行理论描述的有力工具。在此基础上，我们提出用模拟退火法研究几种氢键分子团簇的结构和能级。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来获得热力学性质。与蒙特卡罗方法不同的是，量子蒙特卡罗方法是完全量子力学的，因此可以正确而严格地同时处理振动自由度、非谐性和隧道效应。这项研究将严格地将量子效应包括在用真实粒子间势描述的分子团簇的热力学性质中。同时，它将涉及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。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具有重要意义。因此，理论描述将有助于理解大分子体系中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.