https://qtcovi.github.io/tag/non-covalent-interactions/Non-Covalent InteractionsHugo Blox Builder (https://hugoblox.com)en-usMon, 01 Jan 2024 00:00:00 +0000https://qtcovi.github.io/media/icon_hu11734318148517933569.pnghttps://qtcovi.github.io/tag/non-covalent-interactions/https://qtcovi.github.io/research/electron-correlation-descriptors/Mon, 01 Jan 2024 00:00:00 +0000https://qtcovi.github.io/research/electron-correlation-descriptors/<h2 id="overview">Overview</h2> <p>A key insight driving our research is that the <strong>statistics of the electron number distribution</strong> in real-space atomic basins contain rich information about electron correlation and chemical bonding.</p> <p>By computing the probability of finding <em>n</em> electrons in basin Ω, we obtain:</p> <ul> <li>The <strong>average electron population</strong> <em>N</em>(Ω) — the QTAIM atomic charge.</li> <li>The <strong>variance</strong> — a measure of electron fluctuation and localisation.</li> <li>The <strong>delocalization index</strong> δ(A,B) — the covariance of electron populations between basins A and B, providing an orbital-invariant bond order.</li> <li>Higher-order <strong>cumulants</strong> — sensitive to multi-centre bonding and electron correlation beyond mean-field.</li> </ul> <h2 id="non-covalent-interactions">Non-Covalent Interactions</h2> <p>We use delocalization indices, variance maps, and IQA inter-atomic energies to characterise and classify non-covalent interactions (hydrogen bonds, halogen bonds, van der Waals, π–π stacking) without reference to molecular orbitals.</p> <h2 id="beyond-dft">Beyond DFT</h2> <p>Our descriptors are applicable with any level of theory (HF, DFT, CISD, CCSD, CASSCF, Quantum Monte Carlo), allowing direct assessment of the effect of electron correlation on bonding descriptors.</p>