2.2 f-T-P model
In this work, the f-T-P models are established to describe the relationship of properties (density, viscosity and thermal conductivity) with temperature and pressure. Thef-T-P (ρ-T-P , η-T-P , λ-T-P ) model shown as Eq. (1) was used at present for this study. The fitting parametersα , β , γ and χ , used to calculate the density, viscosity and thermal conductivity of ILs are given in Supporting Information Figures S1~ S3.
In structure-property relationship, α is related to the structures of ILs and the parameters β , γ and χ are obtained by two methods: (1) β , γ and χ are set as constants for all ILs; (2) β , γ and χ are variables related to the molecular structure. To compare these two approaches, the density, viscosity and thermal conductivity samples with multiple data points are fitted using Eq. (1) by the above two methods. The calculated results are depicted in Figures 1-3. It can be seen that the second method results in Figure 1 (b), Figure 2 (b) and Figure 3 (b) are better than the first method results in Figure 1 (a), Figure 2 (a) and Figure 3 (a). The correlations between the calculated and experimental values for each sample using the second method are presented in the supporting information. Compared with the first method, the average absolute relative deviation (AARD ) of the second method reduced by 76 %, 79 % and 70 % for ρ , η and λ , respectively. Accordingly, the above calculation results demonstrated that β ,γ and χ adjusted by the molecular structures are necessary and efficient.