9 Comment on “ An optimized potential for carbon

5 Germany 6 In a recent article, Zhang and Duan [1] presented a new potential model 7 for carbon dioxide (CO 2). It consists of three Lennard-Jones (LJ) sites to 8 account for repulsion and dispersion and three distributed partial charges to 9 describe the quadrupolar interaction. The molecular model is rigid and ro-10 tationally symmetric around the molecular axis. In that work [1], simulation 11 results on vapor-liquid equilibria (VLE), radial distribution function and self-12 diffusion coefficient have been reported for the new CO 2 model which are in 13 excellent agreement with experimental data. They also compared to results 14 from different other models from the literature. The new model is found " to be 15 superior to the previous models in general ". 16 For the VLE properties, deviations between model and experimental data 17 are reported to be [1]: 0.7 % for vapor pressure, 0.1 % for saturated liquid 18 density, 2.3 % for saturated vapor density, and 1.9 % for heat of vaporization. 19 Particularly for vapor pressure, which is the most sensitive of those proper-20 ties, the authors claim to achieve an average accuracy of better than 1 % over 21 the entire temperature range with a molecular model which is noteworthy for 22 any molecular model.