Theoretical Evaluation Of Apparent Polarization Energy Of Organic ?-conjugated Acene Molecular Charge Carrier Condensate Phase

The knowledge of polarization energy of charge carriers in condensed phase plays an important roles in understanding and designing organic electronics devices.The polarizable force field(PFF)is one of the practical approaches to efficiently calculate polarization energy of organic crystals and disordered systems.And the performance of PFF can be evaluated with respect to the corresponding experimental IP and EA values.However,it is difficult to get reliable charge carriers' energy of crystals from experiments.Thus,it is necessary to use a QM-based method to evaluate the performance of PFF on electronic polarization process.In this thesis,I use the block-localized wavefunction(BLW)coupled with density functional theory(DFT)method to solve electronic polarization energies of some oligoacenes prototype models,which are used as references to evaluate the performance of the AMOEBA PFF.Furthermore,AMOEBA PFF was applied to the calculation of apparent polarization energy(EP)in molecular crystal materials.The details are showed as follows:Chapter one:The theoretical background of the electron transfer for organic conjugated molecules is briefly introduced;the definition of electronic polarization energy is described in detail from the perspective of quantum mechanics and electrons.At the same time,the research progress of apparent polarization energy is described from both experimental and theoretical calculations,to determine the development of the first-principles method to evaluate the interaction between charged molecules and the environment.Chapter two:The four kinds of methods such as local charge state of QM,molecular force field(AMOEBA PFF),QM/MM and QM/PCM are briefly compared and reviewed.The advantages and disadvantages of these methods are addressed then.Since the BLW/DFT method can construct the local charge state and obtain the local charge state energy,then providing the QM method to evaluate the parameter optimization of the AMOEBA PFF.The AMOEBA PFF has the low computational cost and the extrapolated calculation of the EP for supramolecular cluster radius up to 50 A.Therefore,we choose BLW/DFT and AMOEBA PFF methods to compute EP of the organic ?-conjugated molecular clusters.Chapter three:We take some clusters of naphtalene(NA)?anthracene(AN)? tetracene(TE)and pentacene(PE)as models as well as the supramolecular system of pentamer and nonamer from its corresponding crystal structure as the object to calculate their EPs using BLW/DFT and AMOEBA PFF method under the same DFT level respectively.This method takes full account of the polarization interactions of the environment on the central molecule.The results indicate that for the selected models,the EPs from AMOEBA PFF and BLW/DFT methods can give very good consistency.In addition,it is reasonable for that the AMOEBA PFF method is used to evaluate the EP of the benzene molecular system from the perspective of electrostatic potential simulation and many-body effects respectively.Chapter four:The two extrapolation methods are applied to obtain the electronic polarization in molecular crystal materials.Compared with spherical summation,the Direct summation can effectively express the anisotropic dielectric tensor and give perfectly linear relationship between the EP and the inverse of cube root of number of molecules(N-1/3)in cluster.The linear regression coefficient R2 approaches 1.In addition,the QTAIM are also used to parameterize the atomic polarizability to avoid the problems that Tinker default atomic polarizability neglecting the effect of electronic states on molecular polarizability.Atomic polarizabilities obtained from QTAIM produce a very closely matching the molecular polarizability for neutral and charged molecules.The deviations between EP from BLW and PFF are much better improved due to using QTAIM atomic polarizability.