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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 2.54A.By disallowing the re-bonding of the Si and O atoms,another defect configuration (ⅢSi/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 1.28eV,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.