NLSDA calculations for H3 on Rh5 including high electric fields: Could linear H3 be stable on Rh-tips?

We present ab initio calculations in non-local spin density approximation for up-right standing linear H3 on a Rh5 pyramid, which simulates a kink site and its nearest neighbours of a (100) oriented Rh-tip, including external homogeneous electrostatic fields. In these calculations all distances between the hydrogen nuclei as well as the distance between linear H3 and the top-most Rh atom have been varied. For zero field linear H3 is found to be unstable on Rh5 in agreement with experiments. For fields between 2 and 3 V/Å linear H3 is predicted to be stable. The energy barrier for H3 dissociating from Rh5 decreases gradually with increasing field until it vanishes at 3 V/Å. These theoretical predictions disagree with experimental results. The possibility of triangular H3 is addressed.