The quantity $w^N\left(\mathbf{r}\right)=\left({1/k}^2{T}_{\mathrm{el}}\right)\left[\partial n\right(\mathbf{r}{,T}_{\mathrm{el}})/\partial T_{\mathrm{el}}{]}_{v\left(\mathbf{r}\right),N}$ is introduced as a convenient measure of the local isoelectronic reactivity of surfaces. It characterizes the local polarizability of the surface, and it can be calculated easily. The quantity $w^N\left(\mathbf{r}\right)$ supplements the charge transfer reactivity measured, e.g., by the local softness to which it is closely related. We demonstrate the applicability and virtues of the function $w^N\left(\mathbf{r}\right)$ for the example of hydrogen dissociation and adsorption on Pd(100).

• Received 14 February 1996

DOI:https://doi.org/10.1103/PhysRevLett.77.1560