Abstract
We calculate the optical response of silicon, (ω), below the optical-absorption threshold and the static dielectric constant of germanium. The time-dependent local-density approximation (LDA) is modified by the addition of a self-energy term taken to be a ‘‘scissors operator,’’ . This form leads to a Ward identity replacement p→(- (-)p. For silicon, we obtain 11.3 for (ω=0), compared to 11.7 for experiment, 13.1 in our LDA calculation, and 8.4 in a naive self-energy corrected theory (i.e., simply modifying the eigenvalues without modifying the momentum operator). For germanium, the corresonding values as 16.5, 15.8, 21.3 and 10.4
- Received 11 September 1989
DOI:https://doi.org/10.1103/PhysRevLett.63.1719
©1989 American Physical Society