Effect of van Hove Singularity on T c in Rb doped C 60
B.K. Agrawal, S. Agrawal, P.S. Yadav, P. Srivastava, R. Srivastava and S. Singh
Physics Department, Allahabad University Allahabad-211002, India
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Received: January 13, 2003; revised version April 13, 2003
In the present study we investigate the role of van Hove singularity on the optimization of T c in Rb doped fullerenes C 60 Rb 3 . A first principles self-consistent full potential linear muffin-tin orbital method using density functional theory in local density approximation was employed. The doped Rb atoms are of two types occupying the tetrahedral and interstitial positions in the fcc lattice. The added Rb atoms fill the t 1u band of the undoped fullerenes C 60 up to half which makes C 60 Rb 3 conducting. Saddle points leading to van Hove singularities are observed in the neighbourhood of the symmetry point L. The shifting of the van Hove singularity with the volume of the lattice is investigated. We observe a saddle point just at the Fermi level for a lattice constant of 14.435 A. The highest value of T c should thus be observed at the above lattice constant. This result is in excellent agreement with the observed high value of T c measured in C 60 Rb 3 for a lattice constant of 14.435 A.
DOI: 10.12693/APhysPolA.103.477
PACS numbers: 74.25.Jb, 74.62.Fj, 74.70.Wz