Within density-functional theory, we compute the Born effective charges of tungsten trioxyde in its reference cubic phase (defect-perovskite structure). For the tungsten atom, the effective charge tensor is isotropic, with $Z_{\mathrm{W}}^{*}=+12.51\mathrm{}$. For the oxygen atoms, the two independent components of the tensor, corresponding, respectively, to a displacement of the atom parallel or perpendicular to the W-O bond, have the values $Z_{\mathrm{O}\Vert }^{*}=-9.13$ and $Z_{\mathrm{O}\perp }^{*}=-1.68$. $Z_{\mathrm{W}}^{*}$ and $Z_{\mathrm{O}\Vert }^{*}$ are anomalously large with respect to the nominal ionic charges $(+6\mathrm{}$ on W and $-2$ on O), but compatible with the Born effective charges found in related ABO${}_3$-perovskite compounds.

• Received 15 January 1997

DOI:https://doi.org/10.1103/PhysRevB.56.983