The temperature evolution of structural effects associated with charge (CO) and spin order (SO) in La_1.67Sr_0.33NiO_4 has been investigated using neutron powder diffraction. We report an anomalous shrinking of the c/a lattice parameter ratio that correlates with T_ CO. The sign of this change can be explained by the change in interlayer Coulomb energy between the static stripe-ordered state and the fluctuating stripe-ordered state or the charge-disordered state. In addition, we identify a

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... ibution to the mean-square displacements of Ni and in-plane O atoms whose width correlates quite well with the size of the pseudogap extracted from the reported optical conductivity, with a non-Debye-like component that persists below and well above T_ CO. We infer that dynamic charge-stripe correlations survive to T∼2T_ CO