Evaluation of the thermodynamic data of CH₃SiCI₃ based on quantum chemistry calculations

CH₃SiCl₃ (methyltrichlorosilane) (MTS) is one of the most important precursors for manufacturing both an oxidation resistant SiC coating and a functional SiC film by chemical vapor deposition (CVD). In order to analyze the decomposition products of MTS with a thermodynamic calculation, correct thermodynamic data must be obtained from the authoritative data sources. G3(MP2) has been applied to evaluate the thermodynamic data of MTS (gas). The calculated value of the Gibbs energy of formation, Δ_fG _ro⁰(298.15 K)=-490.13 kJ-mol^-1, compares with a value, Δ_fG_m⁰(298.15 K) =-468.02 kJ·mol^-1 from the 4th edition of the NIST-JANAF Thermochemical Tables. Further analyses have been conducted: (1) by using G3, G3//B3LYP, and G3(MP2)// B3LYP theories; (2) by using variable scale factors for G3(MP2) theory; and (3) by investigating the accuracy of both experimental and calculated thermodynamic data. The calculated values can provide Δ_fG_m⁰ values for MTS above 1500 K. The final fitted equation for MTS(gas) is: Δ_fG_m ⁰=7.5763 ×10^-6T²+1.9649 × 10 ^-1T-5.4817 ×10², where T is absolute temperature.