Schrödinger, slowly.
The postulates, the electronic Hamiltonian, the Born interpretation. One minimal example (the particle in a box) solved both analytically and numerically.
Read chapter 01 →Reader-first knowledge base
Density Functional Theory, reader-first.
A progressive walk through the foundations, methods, and practice of DFT — from the postulates of quantum mechanics to the Kohn–Sham equations, exchange–correlation functionals, and the modern zoo of practical approximations.
# Restricted Kohn–Sham SCF loop.
def ks_scf(n_elec, v_xc, max_iter=100):
"""Return the converged density + KS eigenvalues."""
P = initial_guess(n_elec)
for it in range(max_iter):
J = hartree_from(P)
F = H_core + J + v_xc(P)
ev, C = diagonalise(F, S)
P_new = density_from(C, n_elec)
if converged(P, P_new):
return energy(P), ev, C
P = mix(P, P_new, α=0.3)
raise RuntimeError("SCF did not converge")What you'll find
Six chapters, one continuous argument.
Every chapter follows the same template: the claim, the derivation, a minimal code sample, and an honest list of what the formula doesn't tell you. Math is rendered client-side; code is Python unless otherwise noted.
The exponential wall.
Why the exact electronic wavefunction is unsolvable for any non-trivial molecule, and a tour of the hierarchy that tries to fix it: CI, MP2, CCSD(T), full CI.
Read chapter 02 →Hartree–Fock, then Kohn–Sham.
Mean-field theory and the self-consistent field — the vocabulary every later method is forced to speak. Then the Kohn–Sham reformulation that hides the unknown inside a single functional.
Read chapter 03 →The future plan
A canvas e-reader for the chapters.
The current site is plain Jekyll. The future plan is a
custom e-reader surface — @chenglou/pretext
for the layout (faster than DOM measurement), KaTeX for
math, light/dark themes, and a font-size slider. The full
system is documented in the
design spec
at the root of the repo.
Start reading
Chapter 00 — Welcome.
How to read these notes, the notation we use, the prerequisites, and a short reading list. No equations — that's the only one.