Hello everybody I am trying to calculate the surface energy of (001) cubic CsSnCl3 perovskite, I have read a nice article titled (Comparative First-Principles Calculations of SrTiO3, BaTiO3, PbTiO3 and CaTiO3 (001), (011) and (111) Surfaces), I have calculated total energies of the bulk and slabs of two terminations (CsCl and SnCl2), then I followed 1, 2 and 3 in the paper but the result is not reasonable and I do not know where I am doing wrong. I have did calculation as follow: 1. I have calculated total energies of the bulk and slabs (Both relaxed and unrelaxed) and converted it to Joule. 2. Applying equation 1 to calculate unrelaxed energy. I have 45 atoms in both slabs together (22+23) and 5 atoms in the bulk so N is 9. 3. I have followed equations 2 and 3. Any help or tip will be approciated. Thanks in advance Best regards Nawzad A.
Dear Nawzad A. Abdulkareem,
If I understand correctly your question, your calculated surface energy is different from literature. If you have different termination in both sides, you cannot find exact surface energy. To calculate exact surface energy, you need to create the termination for both side of the slab. For that I recommend to delete one layer from bottom or upside to create the same termination for both side. Firstly, the same termination helps to avoid dipole interaction between each sides of slab (you can check by calculating the total energy by increasing vacuum thikness. if there is dipole interaction, you cannot achieve convergance in total energy in various vacum thickness).
In some literatures, in calculation of surface energies they use different methods.
To calculate surface energy, I recommend this simpler way:
1. Calculate total energy of bulk CsSnCl3.
2. Create surface slab with 15 A vacum thickness (1x1x6, 2x2x6 or you can choose). If you want to study 001 surface so don't use less that 6 layers along z axis. CsSnCl3 looks like CsCl and SnCl2 layers in super cell you can see. If you want to create CsCl termination in both side delete SnCl2 layer from your bottom of slab structure. If you want SnCl2 termination, delete CsCl layer from upside of slab structure. then you have slab two structure: CsCl or SnCl2 termination.
3. Calculate the total energy of both slab structure.
4. Find stable structure of CsCl and SnCl2 and calculate their total energies.
5. if you have 1x1x6 slab, you can calculate surface energy using this equation: For CsCl termination: Es,cscl=(6*Ebulk-Eslab,cscl-ECsCl)/2A, For SnCl2 termination: Es,sncl2=(6*Ebulk-Eslab,sncl2-Esncl2)/2A.
Sincerely ,
Jasurbek Gulomov
Dear Jasurbek Gulomov
Thanks for your reply
Yes, it does not agree with the literature
I make two slabs, each has same terminations at the both sides, CsCl and SnCl2, each slab has nine layers and about 20 Angstrom vacuum at each side
Sincerely ,
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