Extended bond orbital theory of piezoelectric and transverse charges

Extended bond orbitals are used to calculate the transverse charge and piezoelectric charge in cubic semiconductors. For both optical mode splitting and piezoelectricity, it gives improved agreement with experiment over the bond orbital model. It also clarifies the significance of the dimensionless quadrupole $\Delta Q_{\mathrm{xyz}}$. The success of this calculation gives additional support for the use of linear combination of atomic orbitals theory with universal parameters.