Ab Initio Study of the Dynamical Si–O Bond Breaking Event in α-Quartz**Supported by the National Natural Science Foundation of China under Grant Nos 10744048 and 11202032, and the Defense Industrial Technology Development Program of China under Grant No B1520132013.

Abstract

The Si–O bond breaking event in the α-quartz at the first triplet (T1) excitation state is studied by using ab initio molecular dynamics (AIMD) and nudged elastic band calculations. A meta-stable non-bridging oxygen hole center and E′ center (NBOHC-E′) is observed in the AIMD which consists of a broken Si–O bond with a Si–O distance of 2.54 Å. By disallowing the re-bonding of the Si and O atoms, another defect configuration (III-Si/V-Si) is obtained and validated to be stable at both ground and excitation states. The NBOHC-E′ is found to present on the minimal energy pathway of the initial to III-Si/V-Si transition, showing that the generating of the NBOHC-E′ is an important step of the excitation induced structure defect. The energy barriers to produce the NBOHC-E′ and III-Si/V-Si defects are calculated to be 1.19 and 1.28 eV, respectively. The electronic structures of the two defects are calculated by the self-consistent GW calculations and the results show a clear electron transition from the bonding orbital to the non-bonding orbital.