Add DFT book to resources (#991)

Co-authored-by: Niklas Schmitz <niklas.f.schmitz@gmail.com>

docs/Project.toml

@@ -29,4 +29,4 @@ WriteVTK = "64499a7a-5c06-52f2-abe2-ccb03c286192"
 wannier90_jll = "c5400fa0-8d08-52c2-913f-1e3f656c1ce9"
 
 [compat]
-Documenter = "~1.2"
+Documenter = "~1.5"

docs/src/guide/introductory_resources.md

@@ -34,6 +34,14 @@ see [Publications](@ref).
   in particular the [summary of DFT theory](https://michael-herbst.com/teaching/2022-mit-workshop-dftk/2022-mit-workshop-dftk/DFT_Theory.pdf).
 
 ## Textbooks
+
+- [Density Functional Theory](https://doi.org/10.1007/978-3-031-22340-2)
+  edited by Eric Cancès and Gero Friesecke (Springer, 2023):
+  Up to date textbook accessible to an interdisciplinary audience with contributions
+  by mathematicians and application researchers. Particularly relevant are:
+    * [Chapter 1: Review of Approximations for the Exchange-Correlation Energy in Density-Functional Theory](http://arxiv.org/abs/2103.02645v1)
+    * [Chapter 7: Numerical Methods for Kohn–Sham Models: Discretization, Algorithms, and Error Analysis](https://doi.org/10.1007/978-3-031-22340-2_7)
+
 - [Electronic Structure: Basic theory and practical methods](https://doi.org/10.1017/CBO9780511805769)
   by R. M. Martin (Cambridge University Press, 2004):
   Standard textbook introducing

examples/gross_pitaevskii.jl

@@ -50,7 +50,7 @@ model = Model(lattice; n_electrons, terms, spin_polarization=:spinless);  # spin
 # We discretize using a moderate Ecut (For 1D values up to `5000` are completely fine)
 # and run a direct minimization algorithm:
 basis = PlaneWaveBasis(model, Ecut=500, kgrid=(1, 1, 1))
-scfres = direct_minimization(basis, tol=1e-8) # This is a constrained preconditioned LBFGS
+scfres = direct_minimization(basis; tol=1e-8) # This is a constrained preconditioned LBFGS
 scfres.energies
 
 # ## Internals