The valence band offsets ΔE_v(x) as a function of the alloy compositon x of two typical lattice matched ternary alloy heterojunctions (AlP)_x(Si₂)_1-x/GaP and (GaP)_x(Si₂)_1-x/GaP are studied by using the average bond energy theory in conjunction with the cluster expansion method.It is shown that the variations of ΔE_v(x) at (AlP)_x(Si₂)_1-x/GaP and (GaP)_x(Si₂)_1-x/GaP are nonlinear and non monotonous.The calculated results of ΔE_v are in very good agreement with the data previously reported.

Based on an ab initio pseudopotentials band structure method,a theoretical approach of tak-ing the average-band energy as a energy reference is suggested to determine the valence-band offsets at Si/Ge heterojunctions under three different strain conditions:using Si as a substrate,using Ge as a substrate and Si-layer,Ge-layer deforming freely.The results are 0.731eV,0.243eV and 0.521eV respectively,in good agreement with relevant experimental values.

On the basis of LMTO-ASA band calculation method, the electronic structure of (Ba_1-xK_x)BiO₃ system was obtained by using a virtual crystal approximation (VCA) in which the atomic sphere radii and potential parameters in different compositions are determined by linear interpolation. We contrast the composition dependence of the VCA electronic structure with those of the expended unit cell method. It is shown that the VCA method was valid for such a complex system. The accuracy of our LMTO-ASA-VCA results is also discussed.

The features and functions of both the empty atom-spheres and atomic empty d-states in linearized muffin tin orbital (LMTO) band structure calculations for sp³-semiconductors are investigated. A new approach, in which the states associated with atomic empty d states and empty-sphere p and d states are only incorprated in the evaluation of matrix elements is suggested. The method is spplied to study the band struture of gaAs as a test case. It is shown that the convantional secular determinant with a size of 36×36 can be reduced to a much smaller one with a aize of 10×10 and the results are still quite reasonable.