Au40: A large tetrahedral magic cluster

40 is a magic number for tetrahedral symmetry predicted in both nuclear physics and the electronic jellium model. We show that Au-40 could be such a a magic cluster from density functional theory-based basin hopping for global minimization. The putative global minimum found for Au-40 has a twisted pyramid structure, reminiscent of the famous tetrahedral Au-20, and a sizable HOMO-LUMO gap of 0.69 eV, indicating its molecular nature. Analysis of the electronic states reveals that the gap is related to shell closings of the metallic electrons in a tetrahedrally distorted effective potential.