COMPUTER-SIMULATION STUDY OF PRESSURE-INDUCED STRUCTURAL-CHANGES IN YBA2CU4O8

Pressure-induced structural changes in YBa2Cu4O8 have been studied for pressures up to 10.5 GPa using atomistic simulation techniques. The calculated results are generally in good agreement with experiment. Our calculations show that the in-plane copper to apical oxygen distance Cu(2)-O(1) decreases to a greater extent than the compression of the lattice parameter c and that its compressibility decreases as pressure increases. However, no evidence of a direct dependence of T(c) on the Cu(2)-O(1) distance was found. A very small reduction in the distance between the in-plane copper located on both sides of the yttrium (Cu(2)-Cu(2)) was observed. Following earlier studies we propose that this effect may be correlated with the pressure dependence of T(c). Based on our calculated pressure-dependence of the structural data, this model yields a value for dT(c)/dP of 5.56 K GPa-1 which is in excellent agreement with the observed values in the pressure range of 0-4 GPa.