摘要The lattice dynamics of rhombohedral CaC6 is studied as a function of pressure to probe its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressure-induced phase transition in CaC6 is attributable to the softening transverse acoustic (TA) phonon mode at the zone boundary X (0.5, 0.0, 0.5) point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA(X). The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m.
Abstract：The lattice dynamics of rhombohedral CaC6 is studied as a function of pressure to probe its high pressure phase with low superconducting transition temperature using the density functional liner-response theory. The pressure-induced phase transition in CaC6 is attributable to the softening transverse acoustic (TA) phonon mode at the zone boundary X (0.5, 0.0, 0.5) point. The high pressure phase is then explored by performing fully structural optimization in the supercell which accommodates the atomic displacements corresponding to the eigenvectors of the unstable mode of TA(X). The high-pressure phase is predicted to be a monoclinic unit cell with space group P21/m.
LI Yan;ZHANG Li-Jun;CUI Tian;LIU Yan-Hui;MA Yan-Ming;ZOU Guang-Tian. First-Principles Prediction of High-Pressure Phase of CaC6[J]. 中国物理快报, 2007, 24(6): 1668-1670.
LI Yan, ZHANG Li-Jun, CUI Tian, LIU Yan-Hui, MA Yan-Ming, ZOU Guang-Tian. First-Principles Prediction of High-Pressure Phase of CaC6. Chin. Phys. Lett., 2007, 24(6): 1668-1670.
[1] Fogel F L and Herold A 1977 Intercalation Compounds ofGraphite (Lausanne: Elsevier) [2] Dresslhaus M S 1986 Intercalation in Layered Materials, NATOASI Series B: Physics (New York: Plenum) vol 148 [3] Hannay N B et al 1965 Phys. Rev. Lett. 14 225 [4] Weller Th E et al 2005 Nature: Physics 1 39 [5] Emery N et al 2005 Phys. Rev. Lett. 95 087003 [6] Lamura G et al 2006 Phys. Rev. Lett. 96 107008 [7] Mazin I I 2005 Phys. Rev. Lett. 95 227001 [8] Calandra M and Mauri F 2005 Phys. Rev. Lett. 95 237002 [9] Gauzzi A et al 2006 cond-mat/0603443 [10] Smith R P et al 2006 Phys. Rev. B 74 024505 [11] Zhang L et al 2006 Phys. Rev. B. 74 184519 [12] Kim J S, Boeri L and Kremer R K 2006 cond-mat/0603530 [13]Baroni S et al http://www.pwscf.org/ [14] Perdew J P and Burke K 1996 Int. J. Quantum Chem. S 57309 [15] Vanderbilt D 1990 Phys. Rev. B 41 R7892 [16] Laasonen K et al 1993 Phys. Rev. B 47 10142 [17] Monkhorst H J and Pack J D 1976 Phys. Rev. B 13 5188 [18] Marzari N et al 1999 Phys. Rev. Lett. 82 3296 [19] Murnaghan F D 1944 Proc. Natl. Acad. Sci. USA 50697 [20] von der Osten W and Dorner B 1975 Solid State. Commun. 16 431 [21] Baroni S et al 2001 Rev. Mod. Phys. 73 515 [22] Liu A Y and Wentzcovitch R M 1994 Phys. Rev. B 5010362
2007, Vol. 24 
