STRUCTURE, ENERGETICS, AND THERMODYNAMICS OF HYDROGEN BONDED MOLECULAR CLUSTERS

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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 Classical 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 interparticle potentials. At the same time, it will address several important aspects 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 specific regions of macromolecular systems.