Cluster structure, zero temperature

In the third example we shall compare structural details of connectivity in water, either in clusters or in the liquid. This example is given to warn on transferring conclusions obtained from clusters to the liquid. Indeed, we shall show that, whereas in the clusters at zero K temperature, closed ring or 3D-type structures are the most stable ones, in the liquid, at finite temperature, three-dimensional networks are the predominant configurations. 

In this paper we will show that quantum chemistry provides suitable approaches to extracting the specific properties of small metallic and mixed nonstochiometric clusters which cannot be obtained by more approximate methods. This accuracy is needed for controlling the properties through size, shape and composition of the cluster. For this purpose the methodological aspects will be briefly sketched in Section 2.2. We will first address the methods used for the determination of cluster structures at zero temperature and outline the ab initio molecular dynamics method which we developed for the determination of temperature-dependent ground-state properties. Then, ab initio methods for calculation of excited states valid at T = 0 will be described. 

Gradient-based Methods for Determination of Cluster Structures at Zero Temperature... 

Early Car-Parrinello molecular dynamics simulations of small silicon clusters Si (n< 10) have been carried out to obtain zero temperature structures and structural properties at finite temperature [118]. 

The ab initio determination of optically allowed transitions and their intensities for the most stable cluster structures is feasible in particular for simple metals (la) " as well as for mixed aggregates involving metallic, ionic, or polar bonding and combination, of these bonding types. A comparison of the theoretical predictions which are strictly valid at zero temperature with the spectra recorded at low temperature allows one to propose the assignment of the cluster structure to the measured features and to account for the specific character of small finite clusters. 

---