Computational studies of gas-phase Ca3P2 and Ca6P4

Area of Science:

• Computational Chemistry
• Materials Science
• Solid-State Physics

Background:

• Understanding the electronic and molecular structures of calcium phosphides is crucial for predicting their properties.
• Accurate theoretical methods are needed to resolve discrepancies in predicted ground states.

Purpose of the Study:

• To investigate the electronic and molecular structures of Ca3P2 and Ca6P4 using high-level ab initio methods.
• To compare the accuracy of different computational approaches, including DFT and post-Hartree-Fock methods.
• To assess the sensitivity of calculated energetics to basis set variations.

Main Methods:

• High-level ab initio calculations.
• Density Functional Theory (DFT) and post-Hartree-Fock (post-HF) methods.
• Electronic structure and molecular geometry optimizations.

Main Results:

• Ca3P2 exhibits a Jahn-Teller distorted triplet ground state, contradicting DFT predictions of a closed-shell singlet.
• DFT and ab initio methods show consistent relative energies for the Ca6P4 system.
• Calculated energetics are highly sensitive to the size and composition of the calcium basis set, particularly with added valence functions.

Conclusions:

• High-level ab initio methods are essential for accurately determining the ground state of Ca3P2.
• The choice of basis set significantly impacts the reliability of computational studies on calcium phosphides.
• Further theoretical and experimental investigations are warranted to fully elucidate the properties of these materials.