C_6 perturbatively and form level diagram of hetero/homonuclear interactions

[aqfarouk]

Hello,

I tried to compared the results of interaction energy for different types of interacting species and I found something can be interesting. I was trying to compare the values of C_6 calculated perturbatively and the values of C_3 and C_6 from level digram.

If I am not doing the calculations wrong, are there any reasons for the inconsistency of the calculated figures for homonclear interactions with different principal quantum number of Rydberg states (3rd figure), or heteronuclear interactions (4th figure) of Alkali atoms?

1. Interaction between two rubidium atoms in Rydberg state 61s1/2;

2. Interaction between two cesium atoms in Rydberg state 65s1/2;

3. Interaction between two rubidium atoms in Rydberg state 67s1/2 and 69s1/2;

4. Interaction between cesium atom in Rydberg state 61s1/2 and rubidium atoms in Rydberg state 65s1/2;

-Python notebook including the code is attached in the ZIP file.
ARC-Check.pdf
ARC-Check.ipynb.zip