Showcasing different charge mixing methods
- INPUT_1 : broyden mixing with beta=0.7, takes 5 steps to converge
- INPUT_2 : plain mixing with beta=0.7, takes 8 steps to converge
- INPUT_3 : broyden mixing with beta=0.2, takes 6 steps to converge
- INPUT_4 : plain mixing with beta=0.2, takes 37 steps to converge
