A MOLECULAR-DYNAMICS SIMULATION OF AN INFINITE-LAYER COMPOUND ACUO(2)(A=SR,CA)

The stability of an infinite-layer compound ACu(2) (A=Sr, Ca) at high temperature was studied by molecular dynamics simulation. For SrCuO2 t he infinite-layer structure was well reproduced at 300 K. However insp ection of the simulated structure revealed that oxygen ions displaced from initially planar CuO2 layer to the c-direction by +/- 19 pm alter natively. This structure was stable up to 1200 K and transformed to an amorphous phase above 1300 K. For CaCuO2 the infinite-layer structure was unstable even at 300 K. Simulations in which cation in A site was substituted revealed that large cation in A site is responsible for t he stabilization of the structure, consistent with the experimental re sults.