8.06_am_Surprising_Carbon_苏刚.pdf

A Surprising Carbon Gang Su Graduate University of Chinese Academy of Sciences Aug. 6, 2012 Carbon is an old but surprising material. Materials scientists and organic chemists will agree on little but will probably concur that carbon is one of the most intriguing elements in the Periodic Table. Sign of greatest wealth and symbol of persistence (diamond), carbon is at the same time one of the more abundant elements in the universe and on earth. Graphite was the first known semiconductor, coal the driver of industrial revolution, the excessive use of carbon fuels is outbalancing our climate, etc., etc. Synthesis of carbon in a burning star. Two alpha particles react to form beryllium-8. Beryllium-8 and an alpha particle react to form carbon-12, proceeding via the Hoyle state. This state in carbon-12 is a “resonance” in the beryllium-8 plus alpha-particle system. Once the resonant state is formed, it tends to decay by breaking up into beryllium-8 and an alpha particle. However, approximately four out of ten thousand decays bring the excited carbon-12 nucleus to its stable ground state. Graphite Calculated Experimental C=C Bond length (a ) 1.39140 1.42 [7] 0 Total Energy (eV) 4.91359 4.89866 [8, 9] CCC Bond Angle (°) 119.33 120 [10] a conductor Diamond Calculated Experimental C-C Bond length (a ) 1.53635 1.54428 [1] 0 Total Energy (eV) 3.74829 3.704 [2] C C C Bond Angle (°) 109.5 109.5 [2,3] b a c a semico