HFALPHA
HFALPHA = [real]
| Default: HFALPHA | = 6/sqrt(ENMAX)/(2π) | if HFRCUT is 0 |
Description: HFALPHA sets the decay constant used in the method of Massida, Posternak, and Baldereschi, which is activated by HFRCUT=0.
HFALPHA sets the decay constant in the error-function-like charge distribution for the method of Massida, Posternak, and Baldereschi[1]. The error-function-like charge distribution is used to calculate the difference between the isolated probe charge and the periodically repeated probe charge in a homogenous background. The default for HFALPHA is 6/sqrt(ENMAX)/(2π) in atomic units. This usually yields robust and accurate results in the range of meV compared to the Ewald summation used for a regular k-mesh. For more details, see HFRCUT=0.