StructuresandabsorptionopticalspectraofsiliconclusterSi9viafirst-principlescalculations,李哲,陈向荣,Usingafinite-differencepseudopotentialdensity-functionaltheoryinrealspaceandLangevinmoleculardynamicsannealingtechnique,weperformcalculationstodeterminethegrou