Possible typo in DDI formula in documentation

[goodxdie]

Dear spirit developers,

I’ve been performing some DDI-related simulations recently. While checking the Hamiltonian formula on the official website, I noticed it is written as:

$$\mathcal{H}_{\mathrm{DDI}} \propto \frac{(\vec{n}_i \cdot \hat{r}_{ij})(\vec{n}_j \cdot \hat{r}_{ij}) - \vec{n}_i \cdot \vec{n}_j}{r_{ij}^3}$$

However, looking at the source code (e.g., in Hamiltonian_Heisenberg::E_DDI_Cutoff), the implementation includes the factor of 3:

                            Energy[ispin] -= 0.5 * mu_s[ispin] * mu_s[jspin] * mult
                                             / std::pow( ddi_magnitudes[i_pair], 3.0 )
                                             * ( 3 * spins[ispin].dot( ddi_normals[i_pair] )
                                                     * spins[jspin].dot( ddi_normals[i_pair] )
                                                 - spins[ispin].dot( spins[jspin] ) );

This implements the standard DDI tensor:

$$E \propto\frac{3(\vec{n}_i \cdot \hat{r}_{ij})(\vec{n}_j \cdot \hat{r}_{ij}) - \vec{n}_i \cdot \vec{n}_j}{r_{ij}^3}$$

It seems there is a typo in the documentation (the factor of 3 is missing). Could you please check if this is indeed an error in the docs?

Best regards