Validation of the reaction thermodynamics associated with NaSc(BH4)4 from first-principles calculations: detecting...

A critical drawback with first-principles thermodynamic calculations is the absence of the vibrational and entropic contributions to the prediction of reaction mechanisms, which could conclusively show that the predicted reaction mechanism might be not the most stable reaction path. This study focused on providing an answer to this problem by examining possible metastable paths for five reactant mixtures whose reaction mechanisms were previously predicted using first-principles thermodynamic calculations. The aim of this study was to find a minimum free energy path among all the possible paths of each reactant mixture. This effort provided the clear conclusion that the original reaction paths predicted from first-principles thermodynamic calculations were the most stable reaction paths at an appropriate H(2) pressure range for all cases. An additional examination associated with density functional theory uncertainty suggests how the ambiguity of reaction mechanisms predicted based on thermodynamic calculations should be understood and dealt with.