Cluster Analysis : ... Temperature dependent population analyses of clusters can be made!

Exploration of molecular aggregates : Low energy structures are searched very efficiently!

Weakly bound structures such as molecular clusters have many degrees of freedom, and exploration time for the entire search will become too long to handle. GRRM program enables us to explore structures of molecular aggregates very efficiently with the LADDf method.
Structure exploration of molecular aggregates becomes easier, when the following characteristics are considered suitably.
(1) EQonly Option can be used, since TSs are not concerned.
(2) Only the lower energy structures are importnat, an option of Nlowest=n can be used to speed up the exploration.
(3) Populations depend on the temperature. It follows that free enrgy analyses are required as functions of tmeperature.

The above figure shows the results for water molecule octomer obtained by exploration considering the above points with LADD=5, Nlowet=24, at T= 0 - 400 K. Twenty structures from the lowest in free energy (Left top to Right down) are shown at 0 K (Left) and 400 K (Right). At 0 K cube like structures are dominant, while at 400 K multi ring structures are outstanding. Thus, GRRM tells us stability and populations of molecular clusters as functions of temperature.

Thermo-statistical analysis of H+(H2O)8 Cluster

The figure below shows temperature dependent thermal populations of H+(H2O)8 Cluster obtained by an exploration with LADD and Nlowest options. GRRM program can be used to obtain thermodynamic functions by calculating partition functions at a given temperature. In the case of water molecule octomer with one additional proton, cyclic structures are dominant at low temperatures, while at the higher temperature chain structures are preferred. The results were found to agree well with recent experimental findings by spectroscopic studies of clusters.