Silicon surfaces slab model

Fig. 5.14 Side view of a slab model of the surface of amorphous silica [55]. The top surface consists only of Si and O atoms the bottom one is fully hydroxylated. Black, light grey and white spheres are silicon, oxygen and hydrogen atoms, respectively. The large spherical oxygen and all the silicon atoms are to scale with the interatomic distances.

Si atoms representing the dimer structure, four second layer silicon atoms, two third layer silicon atoms, and one fourth layer silicon atom. Although this cluster can be used to simulate the bulk feature of sihcon, the one dimer cluster does not describe the surface reaction adequately [17]. In order to adequately describe the surface at low computational cost, we adopt the three dimer cluster model S121H20. As the energy gain per dimer for the three-dimer cluster is between 0.15-0.20eV and in agreement with the slab results to... 

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