Stable ordered structures of binary technetium alloys from first principles

Technetium, element 43, is the only radioactive transition metal. It occurs naturally on earth in only trace amounts. Experimental investigation of its possible compounds is thus inherently difficult and limited. Half of the Tc-transition-metal systems (14 out of 28) are reported to be phase separating or lack experimental data. Using high-throughput first-principles calculations, we present a comprehensive investigation of the binary alloys of technetium with the transition metals. The calculations predict stable, ordered structures in nine of these 14 binary systems. They also predict additional compounds in all nine known compound-forming systems and in two of the five systems reported with disordered $\chi$ or $\sigma$ phases. These results accentuate the incompleteness of the current knowledge of technetium alloys and should guide experimental studies to obtain accurate structural information on potential compounds, obviating some of the difficulties associated with such work.

Figure 1

The phase-separating or compound-forming characteristics of 28 Tc-transition-metal-alloy systems as found in experiments and in ab initio calculations.