Chemical interactions that govern the structures of metals

Most metals adopt simple structures such as body-centered cubic (BCC), face-centered cubic (FCC), and hexagonal close-packed (HCP) structures in specific groupings across the periodic table, and many undergo transitions to surprisingly complex structures on compression, not expected from conventional free-electron-based theories of metals. First-principles calculations have been able to reproduce many observed structures and transitions, but a unified, predictive theory that underlies this behavior is not yet in hand. Discovered by analyzing the electronic properties of metals in various lattices over a broad range of sizes and geometries, a remarkably simple theory shows that the stability of metal structures is governed by electrons occupying local interstitial orbitals and their strong chemical interactions. The theory provides a basis for understanding and predicting structures in solid compounds and alloys over a broad range of conditions.

Automated summary

Most metals have simple structures, but undergo complex transitions on compression. First-principles calculations can reproduce observed structures and transitions, but a unified predictive theory is lacking. By analyzing electronic properties, a simple theory shows that the stability of metal structures is governed by electrons in interstitial orbitals and their chemical interactions. This theory provides a basis for understanding and predicting structures in solid compounds and alloys.