Photoinduced sp3 Nanosize Domain with Frozen Shear Displacement in Graphite

K. Nishiokaa and K. Nasub aInstitute for Molecular Science, Okazaki, Aichi 444-8585, Japan bSolid State Theory Division, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, 305-0801, Japan

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A novel sp3-bonded nanosize domain, known as a diaphite which is an intermediate state between a graphite and a diamond, is generated by the irradiation of visible laser pulse onto a graphite crystal. The sp3 structure is well stabilized by shear displacement between neighboring graphite layers. We theoretically study the interlayer sp3 bond formation with frozen shear displacement in a graphite crystal, using a classical molecular dynamics and a semi-empirical Brenner potential. We show that a pulse excitation under the fluctuation of shearing motion of carbons in an initial state can generate interlayer sp3 bonds which freeze the shear, though no frozen shear appears if there is no fluctuation initially. Moreover, we investigate a pulse excitation under the coherent shearing motion and consequently obtain that the sp3-bonded domain with frozen shear is efficiently formed. We conclude that the initial shear is important for the photoinduced sp3 nanosize domain formation.

DOI: 10.12693/APhysPolA.121.350 PACS numbers: 64.70.Nd, 61.48.Gh, 31.15.xv, 05.40.-a