Estimation of Properties of Triatomic Molecules from Tabulated Data Using Least-squares Fitting

This paper shows that it is feasible to make rapid forecasts of data for large numbers of molecules by using least-squares smoothing of tabulated data, though the forecasts are not as precise as those from quantum-chemical computation packages which deal with one molecule at a time. The molecules\u27 properties were chosen to be of value in the plasrna and astronomical physics. The work begins with the graphical analysis of critically-analyzed data for ground states of neutral, acyclic, main-group, row 2 to row 6, triatomic molecules to infer a least-squares smoothing equation. The equation is quadratic in a function (R1R2 + R2R3) of the atomic periodnumbers, quadratic in the group number of the central atom, and cubic in the total number of valence electrons. The coefficients of the equation (some of them zero for some properties) were obtained from high-quality tabulated data for the heat of atomization, ionization potential, log of the partition function at 1000 K, and log of the partial-pressure equilibrium constant for the constituent atoms over the diatomic molecules at 1000 K. The equation and its coefficients were tested by comparison with data, from the same tabulations, for·a few molecules not in the original set. Finally, values were forecasted for 164, 145, 107, and 164 additional molecules, for four the properties listed above and in order the same order