1. School
of Semiconductor and Chemical Engineering, Chonbuk National University, 567 Baekje-daero, Deokjin-gu, Jeonju-si, Jeollabuk-do 561-756, Republic of Korea
2. Department
of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, United States
3. Research
Computing Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3420, United States