CHEMICAL TRENDS IN GOLD ALKALI ALLOYS - A DENSITY-FUNCTIONAL THEORY STUDY ON STABILITY AND CHARGE-TRANSFER .1. GOLD ALKALI ALLOYS OF THE FORMULA MAU

Gold alkali alloys have roused the interest of both chemists and physi cists since their discovery half a century ago. While experimentalists tried to synthesize more and more new alloys filling up the homologou s rows of compounds, the theoreticians tried to understand the astonis hing properties of these alloys by doing more and more exact calculati ons. The experimental and theoretical breakthroughs, however, took pla ce only a few years ago, when single crystals could be synthesized and examined and new powerful ab initio programs and supercomputers were developed. Within the framework of density functional theory (in the l ocal density approximation together with norm-conserving, scalar-relat ivistic pseudopotentials) we calculate the structural properties of MA u alloys comparing the stabilities of these alloys in NaCl, CsCl and N aTl structures with each other and with experiment. Moreover, we exami ne the electronic valence charge densities of these alloys and investi gate the charge transfer in them by employing the concept of zero-flux surfaces. We find that charge transfer occurs from the alkali to the gold atom as expected. Moreover, we find a change from ionic to metall ic binding between NaAu and LiAu.