Structure and superconductivity without apical oxygens in (Ca,Na)2CuO2Cl2
D. N. Argyriou, J. D. Jorgensen, R. L. Hitterman, Z. Hiroi, N. Kobayashi, M. Takano
DOI 10.1103/PhysRevB.51.8434 · Physical Review B
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Abstract
Recently superconductivity has been reported in (Ca,Na)2CuO2Cl2 in which the apical anion position was proposed to be occupied by Cl [Hiroi et al., Nature 371, 139 (1994)]. In this paper we report a neutron powder diffraction investigation of nonsuperconducting Ca2CuO2Cl2 and superconducting (Ca,Na)2CuO2Cl2 (Tc=26 K). We confirm that in both compounds the apical anion position is fully occupied by Cl. Unlike the recently reported superconductor Sr2CuO2F2+δ, in (Ca,Na)2CuO2Cl2 we find little evidence for the presence of interstitial atoms. In our structural data the substitution of Na+ for Ca2+ is evidenced by a shortening of the Cu-O bond and lengthening of the Cu-Cl bond. The bond valence of the Cu atom increases, consistent with holes being created by the Na substitution.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| (Ca,Na)2CuO2Cl2 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 26 | Pressure not reported | onset |
| Sr2CuO2F2+δ Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 46 | Pressure not reported | unknown |
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