The Concept of Meta-Accurate Parameters and Its Application to Molecular Structure

A new concept for the determination and representation of molecular parameters is introduced for the general case when experimental and theoretical data are used together in the refinement process. The meta-accurate parameters obtained in this way must fulfill particular criteria related to trueness, precision, and contribution of experimental data. The concept is applied to the field of molecular structure and demonstrated on a particular example. Using experimental rotational constants for arsenic trichloride (AsCl₃) available in the literature, together with the vibration-rotation interaction and electron-mass corrections theoretically predicted in this work, the equilibrium meta-accurate molecular structure (MAMS) parameters were determined by the method proposed here: r_e(As-Cl) = 2.15838(3){61} Å and α_e(Cl-As-Cl) = 98.877(5){40} °, where the numbers in parentheses and curly braces represent accurate total standard deviations in units of the last digit and experimental data contributions in percent, respectively. Applications, advantages, and future perspectives of the concept are discussed.