Hi Mohsen,
epsilon.x computes the matrix elements of the momentum p, which is not easy to augment in a ultrasoft-pp fashion (at variance with operators which are functions of r, i.e. local). According to the size of system you want to study, you may want to generate your own norm-conserving pseudopotentials for Ba and Ti. The other possibility is instead to use the PAW formalism, where the augmentation of p matrix elements is as easy as for r. (of course this would require the generation of the PAW dataset, and some implementation) Related to the program epsilon.x: optical response can be also calculated through the matrix elements of the operator e^(iqr), which can be augmented easily with USPP. Unfortunately, using this solution would require to re-write the program almost from scratch (not recommended). Anyway if you want to follow this possibility, I would then start from a working norm-conserving implementation of it, as the ones in Sax or Yambo hope it helps Andrea BTW: in future posts please remember to add your affilication, according to the "politeness policy" of this forum > Dear users, > at first, i am so sorry that i asked many question about "epsilon.x". > But i faced with "USPP are not implemented", Which means i can not use > ultrasoft pseudopotentials but i want work with Ba and Ti, > is there any another Ref. for pseudopotentials or can i solve this problem in > some way? > Thanks for your reply > Mohsen Modaresi > -- Andrea Ferretti Oxford University, Department of Materials Parks Road, Oxford OX1 3PH, UK Tel: +44 (0)1865 612796; Skype: andrea_ferretti URL: http://quasiamore.mit.edu Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
