https://qtcovi.github.io/tag/iqa/IQAHugo 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/iqa/https://qtcovi.github.io/research/interacting-quantum-atoms/Mon, 01 Jan 2024 00:00:00 +0000https://qtcovi.github.io/research/interacting-quantum-atoms/<h2 id="overview">Overview</h2> <p>The <strong>Interacting Quantum Atoms (IQA)</strong> methodology, developed in our group, partitions the total electronic energy of a molecule rigorously into intra-atomic self-energies and pairwise inter-atomic interaction energies. Each inter-atomic interaction is further decomposed into classical electrostatics and quantum exchange–correlation contributions.</p> <p>Because IQA is grounded in the QTAIM atomic partition, it is invariant to orbital transformations and does not depend on any reference state or arbitrary choices of localisation. This makes IQA particularly valuable for:</p> <ul> <li>Comparing bonding across different molecular environments and bond types.</li> <li>Tracking energy changes along reaction coordinates and conformational changes.</li> <li>Establishing connections between bond strength and electron delocalisation.</li> </ul> <h2 id="iqa-and-bond-orders">IQA and Bond Orders</h2> <p>A central result of IQA analysis is the relationship between the inter-atomic exchange–correlation energy <em>V</em>_XC(A,B) and the classical bond order between atoms A and B. The delocalization index δ(A,B)—the number of electron pairs shared between basins—provides an orbital-invariant bond order.</p> <h2 id="applications">Applications</h2> <p>IQA has been applied in our group to:</p> <ul> <li>Hydrogen and halogen bonds</li> <li>Metal–ligand bonding in transition metal complexes</li> <li>π-stacking and non-covalent interactions</li> <li>Reaction mechanisms and transition state analysis</li> </ul>https://qtcovi.github.io/software/promolden/Mon, 01 Jan 2024 00:00:00 +0000https://qtcovi.github.io/software/promolden/<h2 id="about">About</h2> <p><strong>PROMOLDEN</strong> is our in-house code for the topological analysis of scalar fields derived from the electron density and pair density. It implements:</p> <ul> <li><strong>QTAIM basin integration</strong> — atomic charges, volumes, and energies from IQA.</li> <li><strong>IQA energy decomposition</strong> — intra-atomic self-energies and inter-atomic electrostatic/exchange–correlation interactions.</li> <li><strong>Delocalization and localisation indices</strong> — bond orders from the electron pair density.</li> <li><strong>Non-covalent interaction (NCI) index</strong> — identification and visualisation of van der Waals, hydrogen bond, and steric interaction regions.</li> <li><strong>Electron localisation function (ELF)</strong> — topological analysis of electron pairing.</li> </ul> <h2 id="availability">Availability</h2> <p>PROMOLDEN is available for academic use upon request to the PI. Please contact <a href="mailto:ampendas@uniovi.es">ampendas@uniovi.es</a> to obtain the code and documentation.</p> <h2 id="citation">Citation</h2> <p>If you use PROMOLDEN in published work, please cite:</p> <blockquote> <p>Á. Martín Pendás, E. Francisco, <em>PROMOLDEN: A QTAIM/IQA code</em>, University of Oviedo, 2021.</p> </blockquote>