MONTE-CARLO CALCULATION OF OPTICAL-ABSORPTION BANDS OF A DISORDERED ADSORBATE LAYER

The Monte Carlo (MC) method is shown to be a powerful tool for the inv estigation of IR absorption bands for non-uniform adsorbate layers. Th is method allows one to calculate the band shapes explicitly and accur ately. As input, the method requires information concerning the polari zabilities alpha(omega) of the individual molecules and the matrix of their lateral interactions. The MC calculations reveal the existence o f tiny patterns in the bands that are related to different types of cl usters in the adsorbate layer. The relation between the exact Monte Ca rlo and the conventional coherent potential approximation is discussed . This clearly manifests the advantage of the Monte Carlo method.