Heisenberg kagome 2x2 (12 sites)

Exact energy and best values (rules §6)

exact	-0.4537396	ED Läuchli et al. (2011) · the instance is solved

Energies as E/N (S.S). Classes are different claims and are not ranked against each other.

The Hamiltonian

H = ∑_⟨ij⟩ σ_i·σ_j

Nearest-neighbour Heisenberg antiferromagnet, J = 1, written with Pauli matrices.

lattice: kagome-2x2
sites: 12
boundary: periodic
energies: 1

Stored as a total energy; quoted here as E/N (S.S), which is what the papers report (how the conversion works).

Every published energy

Grouped by what the number is. The exact energy comes first where there is one; in every other group the lowest unflagged energy is its best value, and each row's distance is to that best (rules §6).

Numerically exact (1)

Exact diagonalization, an exact solution, or sign-problem-free QMC where that is established. An exact energy is shown first, before the best of each other class. QMC is exact only within its error bar, which it must state, and reads exact (stochastic); an exact diagonalization outranks it. For a diagonalization resolved by symmetry sector only the ground state's sector is listed; the lowest energies of the other sectors are the instance's spectrum, in its JSON, and are not shown as the exact energy.

E/N (S.S)	distance to class best	σ	Var(E)	V-score	method	source	code	year	comment
-0.4537396exact	0	n/a	n/a	n/a	ED peer reviewed	Läuchli et al. (2011)		2011

How these numbers were read

Where each number below was read, and how it was checked.

-0.4537396, ED

Checked 2026-09-15 · arXiv PDF extracted locally with pypdf in layout mode, parsed by column position and checked against the paper's own per-site column; no LLM transcription

Reported as. Total E = -5.444875216 (S.S), cluster 12

Table I, "Cluster studied in this work", row N = 12: basis vectors a = (2,0), b = (0,2) in units of the kagome lattice vectors a1, a2 (each of length 2a), periodic (torus). E/N = -0.453740 as printed in the table's own E/N column; Pauli total = 4 E. The (2,0),(0,2) cluster is 2 x 2 unit cells, kagome-2x2 in the VarBench naming.

Coverage

Newest published number here: 2011.

This instance as data

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