{
  "size": [1, 1, 1],
  "sites": [{ "kind": "Fe", "position": [0, 0, 0] }],
  "vertices": [
    { "source": 0, "target": 0, "delta": [1, 0, 0] },
    { "source": 0, "target": 0, "delta": [0, 1, 0] },
    { "source": 0, "target": 0, "delta": [0, 0, 1] }
  ]
}