I found a bug in tenes_simple when we consider the biquadratic interaction. The tenes_simple incorrectly creates the biquadratic interaction through SS**2, where SS is a ndarray representing the bilinear Heisenberg coupling. In Python, SS**2 means element-wise multiplication, while the correct biquadratic term should be created by matrix-matrix multiplication.
Please review this update.
I found a bug in tenes_simple when we consider the biquadratic interaction. The tenes_simple incorrectly creates the biquadratic interaction through
SS**2, where SS is a ndarray representing the bilinear Heisenberg coupling. In Python, SS**2 means element-wise multiplication, while the correct biquadratic term should be created by matrix-matrix multiplication. Please review this update.