[Pw_forum] Composition can be replaced by a background charge?

[shuai]

Dear QE users,

I had read a paper about the calculation of NH2CH=NH2PbI3 
(dx.doi.org/10.1021/cm404006p | Chem. Mater. 2014, 26, 1485−1491). In 
this paper, the researcher calculated the electronic structure using 
SIESTA, and the HC(NH2)2 was ignored and a uniform background charge 
density was added to neutralize the charge.
Thus, my question is whether the ESPRESSO can calculate by replacing the 
part of compound (e.g., CH3NH3 or CH(NH2)2) using a uniform background 
charge? Where can I find the tutorials about this?

Thanks in advance.

Best,

Shuai

-- 
PhD student
Graduate School of Life Science and Systems Engineering
Kyushu Institute of Technology, Japan