Congratulations to our PhD students Ivan Giannì, Tommaso Nottoli, and our Postdoctoral researcher Dr. Federica Pes for their publication entitled "Linear Response Equations Revisited: A Simple and Efficient Iterative Algorithm" in the Journal of Chemical Theory and Computation. The Letter presents an algorithm to solve the linear response equations for Hartree-Fock, Density Functional Theory, and the Multiconfigurational Self-Consistent Field method that is both simple and efficient.
The algorithm makes use of the well-established symmetric and antisymmetric combinations of trial vectors but further orthogonalizes them with respect to the scalar product induced by the response matrix. This leads to a standard, symmetric block eigenvalue problem in the expansion subspace that can be solved by diagonalizing a symmetric, positive definite matrix half the size of the expansion space. Numerical tests showed that the algorithm is robust and stable.
The work is available at the following link: https://doi.org/10.1021/acs.jctc.3c00989
