Atomic structure of the CoS$_{2}$(100)-(1$\times$1) Surface

Atomic structure and top-layer relaxation of the CoS$_{2 }$(100) surface are studied by using the quantitative low energy electron diffraction (LEED). From the LEED images, we observed a clear 1$\times $1 pattern with 4-fold symmetry. Over 18 beams of intensities versus energy curves are acquired from the LEED spots. With a series of trial model structures, theoretical intensities computed from full dynamical method are used to compare with experimental data by means of the Pendry R-factor. The clearly favored structural model from the LEED analysis is the 1S-terminated surface, in which the S-S dimmers remain intact and keep a complete S-Co-S sandwich structure. We also find that sub-surface Co and the third layer S atoms relax downward and upward by 0.10 {\AA}, respectively. These results could be compared with other theoretical and experimental studies. *This work was supported by RGC grant No. 8730017 of Hong Kong, Nebraska Research Initiative, the UNL NSF ``QSPINS'' MRSEC (DMR 0213808) and the UMN NSF MRSEC (DMR-0212302).