Analysis of the local structure by single-crystal neutron scattering inLa1.85Sr0.15CuO4

We have determined the anisotropic Debye-Waller parameters of ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_{4}$ with high precision using neutron diffraction on single crystals. The mean-square displacements are explained well by the contribution due to phonons and disorder induced by the mixing of La and Sr ions; the latter was simulated by relaxing the structure locally. Our analysis puts rather low upper boundaries on the amplitude of possible hidden local structural distortions; in particular, there is no evidence for in-plane charge inhomogeneities related to stripe correlations. Further, we conclude that the tilt transition in ${\mathrm{La}}_{1.85}{\mathrm{Sr}}_{0.15}{\mathrm{CuO}}_{4}$ is essentially displacive and continuous in nature.