Temperature dependence of total internal partition sums (q_tot) for various isotopologs of acetylene, displayed over a range from 0 to 1000 K. The isotopologs include ¹³C₂H₂, D¹²C¹³CH, D¹³C¹²CH, C₂D₂, ¹³C₂HD, ¹³CCD₂, and ¹³C₂D₂. Each curve represents the calculated partition sum for one isotopolog, highlighting the effect of isotopic substitution on the partition function as temperature increases. The plot emphasizes how isotopic differences in hydrogen and carbon atoms impact the thermodynamic properties of acetylene across the specified temperature range.