Quantum Calculation for Equation of State of Compressed Solid Argon

Based on the first-principles and using the double cluster with full single and double excitations plus perturbative treatment of triples (CCSD(T)) and the aug-cc-pVQZ basis set, many-body contributions to the cohesive energy, the zero-point vibration energy and the equation of state of solid argon were accurately calculated with the atomic distance R from 0.20 nm to 0.39 nm under high pressure.The results show that the contribution of the many-body interaction to the cohesive energy is an exchange convergent series, and the proportion of the zero-point vibration energy in the total energy is small but by no means negligible.Under high pressure, the compression characteristics of solid argon is over-hardened when only the two-body interaction is considered.By introducing the three-body interaction, the maximum pressure under which our calculations make a satisfactory description of the experiment data can reach 60 GPa.Further, when the four-body interaction is taken into account, the application scope will be expanded to 0-114 GPa.At 114 GPa, the difference between our calculation and that of the experiment is only about 3 GPa, and the relative error is merely 3%.Besides, this work has a broader application scope than the density functional theory, which at present shows a good agreement with the experimental result only in the pressure range of 50-114 GPa.