A method to simulate the dipole moment mode of the scanning nonlinear dielectric microscope (SNDM) has been developed. This method has been applied to the so-called \({\rm Si(111)-(7 \times 7)}\) dimer-adatom-stacking-fault (DAS) structure and a \({\rm Si(111)-(2\times2)}\) surface with one adatom and one restatom, which are the main motifs of the DAS structure. It has been revealed that a local upward dipole moment is observed at the adatom site, consistent with the SNDM experiments. Differences in the local atomic arrangements of the adatom and restatom correlate with the amount of charge transfer between adatoms and restatoms, which varies in concert with the magnitude of the local dipole moment. This method will provide information on local dielectric properties necessary for the interpretation of various surface probe microscopy images.
