Modeling a plethora of dimerized phases in IrTe₂

IrTe₂ is a one of the transition metal dichalcogenides with the structure containing triple triangular layers Te-Ir-Te with Ir ions in the octahedral coordination. Upon cooling below 220 K a sequence of phases with rows of Ir-Ir dimers are seen. Here we combine first principles calculations and a simplified model descibing the free energy of dimerized phases to compute the phase diagram and rationalize the emergence of these phases.