Structure and physical properties of Na4C60 under ambient and high pressures

The structure and physical properties of two-dimensional polymeric Na4C60 (body-centered monoclinic, space group I2/m) are studied in a wide temperature region from 12 to 300 K at 1 bar, and in a pressure region up to 53 kbar at 300 K. The temperature dependence of lattice constants suggests a structural anomaly below 100 K where the variation of spin susceptibility is observed from electron spin resonance. The thermal expansion of the unit-cell volume V is smaller than that of monomeric Rb3C60 and K3C60. The compressibility of c is larger than that of a and b, which can be well explained by the repulsion between Na ions. The compressibility of the center-to-center distance in the (10(1) over bar) plane is similar to1/3 times smaller that that in the (101) plane, which can be well explained by the formation of the polymer chains. Further, a possibility of a three-dimensional polymerization is discussed on the basis of the pressure dependence of C-60. . .C-60 distances.

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This is the institute's copy, as published in Physical Review B, January 2001, Volume 63, Issue 4, Pages 9.
Publisher URL: http://dx.doi.org/10.1103/PhysRevB.63.045418
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