Add two examples

README.md

@@ -87,6 +87,18 @@ python DftbParameterization.py -opt band rep -input dft
     
 - `-input`: folder that contain reference DFT file
 
+As examples, we provide dft/ folder, where dfts.xyz and nitrides.xyz inculde DFT energy/forces for elementary Cu and binary Nitrides as the references, one can try to run commands and repeat the results that we got in the article.
+1. For Elementary Cu
+- make sure that `opt_elem=[]` and `DEFAULT_DFT_FILE=dfts.xyz` in `DftbParameterization.py`, 
+```
+python DftbParameterization.py -opt band rep -input dft/ 
+```
+2. For Binary Nitrides
+- make sure that `opt_elem=[7]` and `DEFAULT_DFT_FILE=nitrides.xyz` in `DftbParameterization.py`
+```
+python DftbParameterization.py -opt band rep -input dft/
+```
+