==== 格子ガス模型 ====
$$
n_{i} = \left\{\begin{array}{l}1\\0\end{array}\right.
$$

$$
{\cal H} = \displaystyle\sum_{i}\varepsilon_{i} n_{i} + \sum_{\langle i, j\rangle}U_{ij} n_{i} n_{j} + \cdots
$$




===== PF3/Ru(001) =====