Structural transition in AuAgTe₄ under pressure

Gold is inert and forms very few compounds. One of the most interesting of those is calaverite AuTe₂, which has incommensurate structure and which becomes superconducting when doped or under pressure. There exist a 'sibling' of AuTe₂, the mineral sylvanite AuAgTe₄, which properties are almost unknown. In sylvanite Au and Ag ions are ordered in stripes, and Te₆ octahedra around metals are distorted in such a way that Ag becomes linearly coordinated, what is typical for Ag¹⁺ , whereas Au is square coordinated-it is typical for d ⁸ configurations, i.e. one can assign to Au the valence 3+. Our theoretical study shows that at pressure [Formula: see text] GPa there should occur in it a structural transition such that above this critical pressure Te₆ octahedra around Au and Ag become regular and practically identical. Simultaneously Te-Te dimers, existing at P  =  0 GPa, disappear, and material from a bad metal becomes a usual metal with predominantly Te 5p  states at the Fermi energy. We expect that, similar to AuTe₂, AuAgTe₄ should become superconducting above [Formula: see text].