Effect of Calcium Doping on the Coordination Polyhedra of PbWO4–PbMoO4 Solid Solutions

The change in the local environment of ions in PbW _1--x MoxO4 solid solutions upon additional calcium doping has been studied. Solid solutions of Pb0.825Ca0.125W _1--x MoxO4 were simulated using the method of empirical interatomic potentials. It is shown that the addition of calcium decreases the unit-cell parameters, volume, and density. The nonlinear behavior of the unit-cell parameter c and volume in dependence of the molybdenum content disappears. Otherwise, the nature of the dependences on the molybdenum content remains: the parameter a and density decrease, while the parameter c and volume increase. With the addition of calcium, the average size of PbO8 polyhedra decreases, while that of MoO4 and WO4 tetrahedra increases. At the same time, the trend in the variation of the polyhedra with increasing molybdenum fraction persists: PbO8 polyhedra increase, while MoO4 and WO4 tetrahedra decrease. In all polyhedra, the difference in interatomic distances increases, indicating their distortion, which may contribute to improving the properties of the material.