{
  "annotation_id": "c419c0c7-89af-46f8-9fc1-81637d6a3f3d",
  "date_created": "2026-03-02T18:01:11.219000Z",
  "date_modified": "2026-03-02T18:01:11.219000Z",
  "file_hash": "c31f6b1c96d9a67b13c5503ae50f7be0791c64841133ebb28b1435950e067f74",
  "private": false,
  "record": {
    "abstract": "In an attempt to improve on our earlier W3 theory [J. Chem. Phys. {\\bf 120},\n4129 (2004)] we consider such refinements as more accurate estimates for the\ncontribution of connected quadruple excitations ($\\hat{T}_4$), inclusion of\nconnected quintuple excitations ($\\hat{T}_5$), diagonal Born-Oppenheimer\ncorrections (DBOC), and improved basis set extrapolation procedures. Revised\nexperimental data for validation purposes were obtained from the latest version\nof the ATcT (Active Thermochemical Tables) Thermochemical Network. We found\nthat the CCSDTQ$-$CCSDT(Q) difference converges quite rapidly with the basis\nset, and that the formula\n1.10[CCSDT(Q)/cc-pVTZ+CCSDTQ/cc-pVDZ$-$CCSDT(Q)/cc-pVDZ] offers a very reliable\nas well as fairly cost-effective estimate of the basis set limit $\\hat{T}_4$\ncontribution. The largest $\\hat{T}_5$ contribution found in the present work is\non the order of 0.5 kcal/mol (for ozone). DBOC corrections are significant at\nthe 0.1 kcal/mol level in hydride systems. . Based on the accumulated\nexperience, a new computational thermochemistry protocol for first-and\nsecond-row main-group systems, to be known as W4 theory, is proposed. Our W4\natomization energies for a number of key species are in excellent agreement\n(better than 0.1 kcal/mol on average, 95% confidence intervals narrower than 1\nkJ/mol) with the latest experimental data obtained from Active Thermochemical\nTables. A simple {\\em a priori} estimate for the importance of post-CCSD(T)\ncorrelation contributions (and hence a pessimistic estimate for the error in a\nW2-type calculation) is proposed.",
    "arxiv_id": "physics/0608123",
    "authors": [
      "Amir Karton",
      "Elena Rabinovich",
      "Jan M. L. Martin",
      "Branko Ruscic"
    ],
    "categories": [
      "physics.chem-ph",
      "physics.comp-ph"
    ],
    "doi": "10.1063/1.2348881",
    "journal_ref": "J. Chem. Phys. 125, 144108 (2006)",
    "title": "W4 theory for computational thermochemistry: in pursuit of confident   sub-kJ/mol predictions",
    "url": "https://arxiv.org/abs/physics/0608123"
  },
  "schema_id": "dorsal/arxiv",
  "source": {
    "execution_id": "9ec225fb-c5e7-4755-abe2-50b566437e24",
    "id": "arXiv Dataset IDs",
    "type": "Model",
    "variant": "snapshot-2026-03-01",
    "version": "0.1.0"
  },
  "user_id": 1000002
}