TY - JOUR
T1 - Oxygen-ordering phenomena in YBa2Cu3O6+x studied by Monte Carlo simulation
T2 - PHASE-DIAGRAM, STRUCTURE FACTOR AND OXYGEN EQUILIBRIUM PRESSURE
AU - Fiig, T.
AU - Andersen, J.V.
AU - Andersen, N.H.
AU - Lindgård, P.-A.
AU - Mouritsen, O.G.
AU - Poulsen, H.F.
PY - 1993
Y1 - 1993
N2 - The oxygen order in YBa2Cu3O6+x has been investigated by Monte Carlo simulation with the two-dimensional anisotropic next-nearest-neighbor lattice gas model, the ASYNNNI model. For a specific set of interaction parameters we have calculated the structural phase diagram, the chemical potential, and the structure factor as a function of temperature and wave vector for x = 0.4. The phase diagram has been determined from an ivestigation of the order parameters and their fluctuations as well as by the use of an improved version of the Ferrenberg-Swendsen method. The calculated phase diagram and the widths of the structure factors are in excellent agreement with measured neutron-diffraction data. We suggest that the observation of an orthorhombic distortion, simultaneously with only short-range oxygen order at T = 25-degrees-C, is due to the freezing-in of an ortho-II domain state with a preferred oxygen chain direction and accordingly only two types of domains. Using thermodynamic relations the chemical potential has been related to the measured oxygen-gas pressure, and it is discussed why only qualitative agreement with experimental data is established.
AB - The oxygen order in YBa2Cu3O6+x has been investigated by Monte Carlo simulation with the two-dimensional anisotropic next-nearest-neighbor lattice gas model, the ASYNNNI model. For a specific set of interaction parameters we have calculated the structural phase diagram, the chemical potential, and the structure factor as a function of temperature and wave vector for x = 0.4. The phase diagram has been determined from an ivestigation of the order parameters and their fluctuations as well as by the use of an improved version of the Ferrenberg-Swendsen method. The calculated phase diagram and the widths of the structure factors are in excellent agreement with measured neutron-diffraction data. We suggest that the observation of an orthorhombic distortion, simultaneously with only short-range oxygen order at T = 25-degrees-C, is due to the freezing-in of an ortho-II domain state with a preferred oxygen chain direction and accordingly only two types of domains. Using thermodynamic relations the chemical potential has been related to the measured oxygen-gas pressure, and it is discussed why only qualitative agreement with experimental data is established.
KW - Materialer med særlige fysiske og kemiske egenskaber
U2 - 10.1016/0921-4534(93)90792-O
DO - 10.1016/0921-4534(93)90792-O
M3 - Journal article
VL - 217
SP - 34
EP - 52
JO - Physica C: Superconductivity and its Applications
JF - Physica C: Superconductivity and its Applications
SN - 0921-4534
IS - 1-2
ER -