Check out the recently published paper on The Density Fitting J + X Approximation in which we use the auxiliary density expansion introduced by Laikov and the Laplacian of the electron density as described by Perdew and Constatin in LL-TPSS as well as Yu, He, and Truhlar in MN15-L. Here we efficiently use these mGGA functionals with only a 10-20% increase in computational cost compared to GGA functionals.
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