Ca neutral clusters: a two-step G ₀ W ₀ and DFT benchmark

Area of Science:

• Computational Materials Science
• Quantum Chemistry
• Condensed Matter Physics

Background:

• Understanding the electronic and structural properties of atomic clusters is crucial for developing new materials and technologies.
• Calcium clusters, in particular, exhibit unique behaviors due to their electronic structure, making them interesting subjects for theoretical study.

Purpose of the Study:

• To investigate the electronic and structural properties of calcium clusters ranging from 2 to 20 atoms.
• To compare the accuracy of density functional theory (DFT) with generalized gradient approximation (GGA) against GW calculations.
• To analyze trends in binding energies, ionization potentials, and electron affinities for calcium clusters of varying sizes.

Main Methods:

• A two-step computational scheme combining GW approximation and DFT with GGA was employed.
• Ground-state structure and binding energies were determined using DFT.
• Electronic properties, including ionization potentials and electron affinities, were calculated using the GW method (G0W0) with an all-electron FHI-aims code.

Main Results:

• GGA calculations overestimated binding energies, geometries, electron affinities, and ionization potentials compared to benchmark GW results.
• Neutral calcium clusters generally show an increasing binding energy trend with size, with exceptions for specific stable clusters.
• The magic cluster Ca10 exhibited a high ionization potential and low electron affinity. Larger clusters showed less variation in ionization potential, while electron affinities increased with size.

Conclusions:

• The GW approximation provides a more accurate description of calcium cluster properties than GGA.
• Distinct trends in electronic properties and binding energies were identified for calcium clusters up to 20 atoms.
• The ionization potentials of calcium clusters, as calculated by G0W0@PBE, represent novel findings not yet documented in existing literature.