The electronic structure of the ladder-chain compound Sr14-xCaxCu24O41 is s
tudied by ab initio calculations within the local density approximation. Th
e effects of Ca substitution and structure modulation on electronic structu
re are discussed. It is found that 0.05 holes per copper atom are on the la
dder layers for fully substituted compound, Ca14Cu24O41. (C) 1999 Elsevier
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