The electronic band structure of a metal can change significantly under different strain conditions, as predicted by density functional theory DFT calculations. Strain can be classified into three types: tensile, compressive, and shear strain. When a metal is subjected to strain, its lattice structure is altered, which in turn affects the electronic properties of the material.DFT calculations can provide insights into the changes in the electronic band structure under different strain conditions. Here are some general trends observed in strained metals:1. Bandgap change: Under tensile or compressive strain, the bandgap of a metal can either increase or decrease depending on the specific material and the direction of the applied strain. This change in bandgap can lead to a transition from a metallic to a semiconducting state or vice versa.2. Band dispersion: The dispersion of electronic bands i.e., the variation of energy levels with respect to the wave vector can be affected by strain. This can lead to changes in the effective mass of charge carriers and, consequently, the electrical conductivity of the material.3. Band alignment: Strain can also alter the relative positions of the valence and conduction bands, which can affect the material's ability to absorb or emit light, as well as its electronic and optical properties.4. Spin-orbit coupling: In some materials, strain can influence the spin-orbit coupling, leading to changes in the electronic band structure and potentially giving rise to novel magnetic and electronic properties.5. Lattice symmetry: Strain can cause a change in the lattice symmetry of a material, which can lead to the appearance or disappearance of specific electronic bands, as well as changes in their dispersion.In summary, density functional theory calculations can help predict how the electronic band structure of a metal changes under different strain conditions. These changes can significantly impact the material's electronic, optical, and magnetic properties, making strain engineering a promising approach for tailoring the properties of materials for specific applications.