Option for low-pass filtering in LDOS

src/scf/chi0models.jl

@@ -16,6 +16,8 @@ For details see Herbst, Levitt 2020 arXiv:2009.01665
 """
 @kwdef struct LdosModel <: χ0Model
     adjust_temperature = IncreaseMixingTemperature()
+    characteristic_length = 0  # in Bohr (0 means low-pass filtering is disabled)
+                               # Good values for filtering are between 2 and 0.1 Bohr
 end
 function (χ0::LdosModel)(basis; eigenvalues, ψ, εF, kwargs...)
     n_spin = basis.model.n_spin_components
@@ -28,6 +30,16 @@ function (χ0::LdosModel)(basis; eigenvalues, ψ, εF, kwargs...)
         return nothing
     end
 
+    if χ0.characteristic_length > 0
+        length_fourier = 2π / χ0.characteristic_length
+        G₀ = 2length_fourier / 3
+        Gslope = length_fourier / 6
+        f_lowpass(G) = (1 - erf((G - G₀) / Gslope))/ 2
+
+        lowpass = [f_lowpass(norm(G)) for G in G_vectors_cart(basis)]
+        ldos = G_to_r(basis, r_to_G(basis, ldos) .* lowpass)
+    end
+
     tdos = sum(sum, ldos) * basis.dvol  # Integrate LDOS to form total DOS
     function apply!(δρ, δV, α=1)
         δεF = dot(ldos, δV) .* basis.dvol

src/scf/mixing.jl

@@ -248,8 +248,8 @@ end
     #       I also tried experimenting with some low-pass filtering in the LdosModel, but
     #       so far without a fully satisfactory result. As of now LdosMixing should be avoided
     #       with potential mixing.
-    @warn("LdosMixing / χ0Mixing not yet fine-tuned for potential mixing. " *
-          "Make sure use use sufficient k-Point sampling. Use at your own risk.", maxlog=1)
+    @warn("LdosMixing / χ0Mixing not yet fine-tuned for potential mixing. You're on your own. " *
+          "Make sure to use sufficient k-Point sampling and maybe low-pass filtering.", maxlog=1)
 
     # Solve ε δV = δF with ε = (1 - vc χ₀) and χ₀ given as the sum of the χ0terms
     devec(x) = reshape(x, size(δF))