Various external factors can influence on the energy-band structure of a solid

the changes of the energy-band structure will result in many novel physical phenomena

which has made people explore many new applied fields and attracted considerable attention in the last several decades. In the middle of the 70's of the 20

th

century

the influences of pressure on the absorption band edge of the semiconductor GaAs have been observed in the experiment. In the early period

some theoretical methods have been developed to investigate dependence of the direct energy gap of GaAs on hydrostatic pressure and optical properties of semiconductors under pressure. Although these theoretical methods have achieved some successes

yet they belong basically to the semi-experience phenomenology and the semi-classical theory. Recently

by using self-consistent pseudopotential method based on density-functional theory

XIAO Qi

etal

. have investigated the electronic structure of iron pyrite FeS

2

under external pressure

it was shown that the forbidden-band width become wider with increase of external pressure. However

the work studying the influence of external pressure on the energy-band structure by using energy-band theory of quantum mechanics is little still. The aim in the paper is to study the influences of pressure on the energy-band structure of a solid by using the tight-binding theory. We have calculated the 1s and 2s energy bands of a body-centered cubic lattice

and discussed the influences of pressure on the energy-band structure. The results show that the pressure makes lattice constant change

which results in the changes of the 1s and 2s energy-band width and the forbidden-band width between two energy bands for the body-centered cubic lattice. From our results

we have calcu-lated concretely the influences of pressure on the energy-band structure of the Li metal

with the increase of the pressure

the 1s and 2s energy-band width of Li metal will widen

the forbidden-band width between the two energy bands will narrow. Compared with the published data

our results are agreement with the experiment results in order of magnitude. In summary

by using the tight-binding theory we have investigated the influence of pressure on the energy-band structure of a solid. We can describe the energy-band width and the forbidden-band width as a function of the distance between neighbour atoms

when the pressure increase

the distance between neighbour atoms will decrease and make the energy-band structure of a solid change

which makes people understand easily the physical essence of the influence of pressure on the energy-band structure of a solid

it is obvious that the tight-binding theory has remarkable advantages in studying the influence of pressure on the energy-band structure of a solid.