  This article explore the behavior of singlet pairs in Inorganic crystals and
take the Ti-Ti and Bi-Bi dimer for example, including the transition in
critical temperture by directly or indirectly. Through the analysis, It is
proposed that with the decrease of temperature, the strength of spin-orbit
coupling (SOC) increases and the phase difference also increases. In the
one-dimensional spin 1/2 chain system of TiOCl and BiOCl crystals, the
possibility of reversible parameter modulation is proposed by the calculation
of the first principle analyzing the process and analysis of the structural
phase transition process. It's shown that the different sturcture transition is
relate to the difference of the dimer structure and the fluctuation of orbital
order through the comparative study of TiOCl and BiOCl.
