CH3NH3PbI3 Perovskite construction

[Hinnes Chan]

Hi, everyone. 

I am new to VESTA. I watched several tutorial videos on YouTube and learnt some basics of the software. My goal is to learn making the tetragonal CH3NH3PbI3. 

So far, I have found the lattice parameters of all components from a paper except hydrogen atoms of CH3 and NH3 molecules. Could anyone help me on that. Please also see the attachment screenshot as reference. 

Moreover, I have downloaded a cif file to compare. It provides parameters of individual atoms in the unit cell. Could anyone explain the difference to me? Why did the cif do it that way but the journal paper I found only give 1 set of parameters for each element?

Thirdly, I tried the NaCl tutorial on YouTube which told me to change the r of atom from default whereas the cif file of the perovskite kept the default values. Why and should I change? I could not find any. 

Kind regards,

Hinnes 

[Cippo Lippo]

Dear Hinnes,

1) The structure you want is available in literature. It happens such material was the topic of my PhD. You can find all the information in my old group page:
http://wmd-group.github.io

The structure are available through github and or attached in some of my studies (google scholar: fede_rico Brivio)

2) With respect to the imagine you post, you must know that the position of the organic molecule is often not-fixed. So it is more useful, in my opinion to build first the fully inorganic higher symmetry CsPbI3, then substitute Cs with N-C and then adding the H.