Quasiorbitals

Quasiorbitals are a concept in quantum mechanics that describes the behavior of electrons in solids, particularly in disordered or amorphous materials. Unlike the well-defined orbitals found in isolated atoms or perfectly ordered crystals, quasiorbitals represent a more generalized description of electron localization and delocalization. They are not true quantum states in the same sense as atomic orbitals but rather a mathematical tool to approximate or understand electron wavefunctions in complex environments.

The term "quasiorbital" suggests something that resembles an orbital but is not perfectly so. This arises because the periodic potential experienced by electrons in a crystal lattice is disrupted in disordered systems. This disruption leads to a breakdown of perfect periodicity, and consequently, the electron wavefunctions no longer exhibit the Bloch theorem's characteristic plane-wave-like behavior. Instead, electrons can become localized in certain regions of the material, or their wavefunctions can be spread out in a more complex, non-uniform manner.

Quasiorbitals are often used in theoretical models to describe how electrons transition between localized and delocalized states, which is crucial for understanding electrical conductivity, optical properties, and other phenomena in amorphous semiconductors and other disordered materials. They can be thought of as localized electron wavepackets that have some characteristics of atomic orbitals but are distorted and influenced by the surrounding disordered environment. The study of quasiorbitals helps physicists and chemists to better predict and explain the electronic properties of materials that are not perfectly crystalline.