Exchange-correlation energy performance

The results presented here were obtained in the framework of DFT by using a modified version of deMon code [43], All calculations were performed within the nonlocal density approximation employing the gradient-corrected functional of Perdew [44] for correlation and that of Perdew and Wang [45] for exchange energy (PPW) respectively. For some species test calculations using the local potential [46] were carried out. 

The calculations are performed within the framework of the Carr-Parrinello molecular dynamics [25, 26]. Our approach is based on the density functional theory with generalized gradient approximations after Becke for the exchange energy [27] and Lee, Yang, and Parr for the correlation energy [28]. Troullier-Martins type... 

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