Gaseous short-range interactions

In the liquid (or the gaseous) state of overlayers on surfaces, the adsorbates cannot pass through each other this gives rise to a limited amount of short-range order. Additionally, there is always some non-zero parallel component of the substrate-adsorbate interaction that will make the adsorbates spend more of their time at one type of location than at others this also is a form of ordering. 

Gases are formed by weakly interacting, nearly isolated particles - atoms or molecules. Interatomic or intermolecular distances continuously change and as a result, gases have no fixed shape or volume and gaseous matter occupies all available space. As far as macroscopic properties of a gas are concerned, they remain identical in any direction because its structure, more precisely, the absence of long- or short-range order, is isotropic. 

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