Advances In Explicit Polarization(X-Pol)method And Its Application

This dissertation is aimed to implement new tools into explicit polarization(X-Pol)method and apply it on searching reaction mechanism in complex reactions.The X-Pol method is a fragment-based quantum chemical method that realizes the internal polarization and intermolecular interactions explicitly.The description of inter-fragment interaction is crucial for X-Pol method.Two models are designed to improve the accuracy of inter-fragment interaction:(1)development of fitted density Coulomb bath model,in which fragments are embedded in the Coulomb bath due to other fragments.The Coulomb bath is represented by fitted density;(2)development of fragment exchange potential,which is a fictitious potential and expressed as a Coulomb screened Slater exchange potential with only one parameter.Inter-fragment Pauli repulsion can be calculated by fragment exchange potential.X-Pol is extended to be reactive,by realizing fragments combining and splitting during MD simulation.Automatic reaction path searching program CARNOT is also introduced in this dissertation.Under the guidance of CARNOT,many reaction pathways are spotted and characterized.