Ab initio calculations of many-body interactions for compressed solid argon.

Area of Science:

• Condensed matter physics
• Materials science
• Computational chemistry

Background:

• Understanding the behavior of solid argon under extreme pressure is crucial for materials science.
• Many-body interactions significantly influence the properties of condensed matter systems.
• Previous studies primarily focused on dimer and trimer interactions in solid argon.

Purpose of the Study:

• To investigate the impact of many-body effects, specifically three- and four-body interactions, on the properties of solid argon at high pressures.
• To accurately model the equation of state for compressed solid argon.
• To extend ab initio calculations for three-body interactions to shorter distances.

Main Methods:

• Utilizing a many-body expansion of interaction energy.
• Employing the coupled-cluster method with single, double, and noniterative triple theory (CCSD(T)) for calculating three- and four-body terms.
• Applying the incremental method for efficient computation of many-body interactions.
• Selecting configurations of argon trimers and tetramers mirroring those in the actual lattice.

Main Results:

• The four-body contribution to the interaction energy in compressed solid argon was estimated for the first time.
• Four-body interactions were found to be repulsive at high densities, effectively counteracting the three-body lattice energy.
• The dimer potential combined with three-body interactions accurately reproduced experimental data for the equation of state up to approximately 60 GPa.
• Incorporating four-body effects extended the agreement with experimental measurements to the maximum tested pressure of 114 GPa.

Conclusions:

• Four-body interactions play a critical role in accurately describing the equation of state of solid argon at high pressures.
• The accurate calculation of many-body interactions is essential for understanding condensed matter behavior under extreme conditions.
• This study provides a more comprehensive theoretical framework for solid argon properties, extending predictive capabilities to higher pressures.