Theoretical Exploration of Crystal Structure and Li Intercalation Mechanism of c-HBC

Abstract

Prediction and control of crystal structure are very important in material science and crystal engineering. Especially, crystal structure and electrochemical property are sensitively related with respect to the performance of thin-film electrical device. In this work, we predicted highly potential polymorphs of contorted hexabenzocoronene (c-HBC) directly from the molecular structure. The crystalline phases with low level of lattice energy, which were thermodynamically stable, were searched with possible packing arrangements of c-HBC molecule in all reasonable space groups using a rigid body approximation. In order to obtain accurate geometry and energy, the selected potential crystalline structures were optimized using density functional theory (DFT) calculations. The verification process was done by comparing experimental X-ray diffraction pattern and morphology. In the crystalline phase precisely representing experimentally synthesized sample, Li-lithiation process of c-HBC was further examined in details by calculating intercalation energy and voltage profile and furthermore identifying intercalation sites.