  We use ab initio calculations to examine thermodynamic factors that could
promote the formation of recently proposed unique oP10-FeB4 and oP12-FeB2
compounds. We demonstrate that these compact boron-rich phases are stabilized
further under pressure. We also show that chromium tetraboride is more stable
in the new oP10 rather than the reported oI10 structure which opens up the
possibility of realizing an oP10-Fe(x)Cr(1-x)B4 pseudobinary material. In
addition to exhibiting remarkable electronic features, oP10-FeB4 and oP12-FeB2
are expected to be harder than the known Fe-B compounds commonly used for hard
coating applications.
