Interaction between two structural blocks and its correlation with superconductivity in SmFeAsO_1-xF_x and SmFe_1-xM_xAsO (M = Co,Ni)

¹ Department of Physics, China Jiliang University - Hangzhou 310018, PRC
² State Key Lab of Silicon Materials, Zhejiang University - Hangzhou 310027, PRC
³ Department of Physics, Zhejiang University - Hangzhou 310027, PRC

^a lzhang@cjlu.edu.cn

Received: 30 April 2010
Accepted: 19 August 2010

Abstract

Based on a block model, we developed a program to calculate the cohesive energy of the whole cell and the combinative energy between the Fe-As block and the Sm-O block in SmFeAsO_1−xF_x and SmFe_1−xM_xAsO (M = Co,Ni). A relationship between the combinative energy and T_c is established, which is similar to the previous reports in cuprate HTSCs to some extent. While the nearly unchanged combinative energy in SmFe_1−xM_xAsO (M = Co,Ni), no matter whether the electron is supposed to be at the Fe, As site or at the centre of the Fe-As layer, indicates an itinerant character in SmOFeMAs (M = Co,Ni), which is severely different from the local carrier picture in the cuprate HTSCs. We suggest that the relationship can be understood by the charge-transfer models. Our results may shed light on the similarities and differences in understanding the superconductivity of the two important kinds of HTSCs.