Quantum Stress: Density Functional Theory Formulation and Physical Manifestation

TL;DR

This paper introduces the concept of quantum stress within density functional theory, explaining how electronic effects influence stress in solids and thin films without lattice deformation, with practical demonstrations and implications.

Contribution

It formulates the concept of quantum stress in DFT and demonstrates its manifestations in bulk and surface stress due to electronic effects.

Findings

Quantum stress can be expressed as al elta n, linking electronic effects to stress.

Charge carriers induce bulk quantum stress in materials.

Quantum confinement leads to surface quantum stress in thin films.

Abstract

The concept of "quantum stress (QS)" is introduced and formulated within density functional theory (DFT), to elucidate extrinsic electronic effects on the stress state of solids and thin films in the absence of lattice strain. A formal expression of QS (\sigma^Q) is derived in relation to deformation potential of electronic states ({\Xi}) and variation of electron density ({\Delta}n), \sigma^Q = {\Xi}{\Delta}n, as a quantum analog of classical Hook's law. Two distinct QS manifestations are demonstrated quantitatively by DFT calculations: (1) in the form of bulk stress induced by charge carriers; and (2) in the form of surface stress induced by quantum confinement. Implications of QS in some physical phenomena are discussed to underlie its importance.