Dimer Crystallization Induced by Elemental Substitution in the Honeycomb Lattice of Ru₁₋<i>_x</i>Os<i>_x</i>Cl₃

Substitution effects of Os for Ru in α-RuCl3 are investigated a wide composition range 0 ≤ x 0.67 Ru1−xOsxCl3 by X-ray and electron diffraction, magnetic susceptibility, heat capacity, Raman spectroscopy measurements. Apart from the Kitaev physics with antiferromagnetic interactions increasing x, rich phase diagram is obtained, which includes an long-range order below 12 K 0.15, dome-shaped spin-singlet dimer 130 0.15 0.40, short-range > 0.40. A dimerization as similarly observed under high pressure occurs phase. It suggested that Ru–Os pairs solid solutions tend to form dimers short bonds trigger first-order transition presence pseudo-threefold rotational symmetry around substituted atom only at low substitutions. This rare example molecular orbital crystallization induced elemental substitution highly disordered system. The substitutions may be related random-singlet state stabilized bond disorder honeycomb net.