.. _userdoc-how-to-per-pair-equivariant-features:

Computing per-pair equivariant features
=======================================

In a `previous example
<https://metatensor.github.io/featomic/latest/how-to/computing-lambda-soap.html>`_, we
computed the :math:`\lambda`-SOAP equivariant descriptor. This tutorial focuses on the
generalization of :math:`\lambda`-SOAP to pairs of atoms rather than single centers. 
Per-pair equivariant features are useful as descriptors for `two-center quantities such 
as the Hamiltonian matrix <https://doi.org/10.1063/5.0072784>`_.

.. include:: ../examples/per-pair-equivariant-features.rst
    :start-after: start-body
    :end-before: end-body