Posterior to the electronic and lattice optimization of the bulk GdTe structure, taken from Materials Project database (3), different surfaces, namely (100), ( ), ( ) and (211) were created each of them having 4 layers. Afterwards, 2×2×1 supercell of each considered surfaces was created followed by electronic optimization. ( The adsorption energy of the H* intermediate involved in HER was calculated from the DFT using the following expression (27, 28):