Charge Density Analysis of Zircon (ZrSiO₄) Using Quantum Crystallographic Methods

Charge density analysis is one important branch of crystallography research. The possibility of studying the electron density of crystal structures from experimental data can yield interesting insights from the perspectives of structural chemistry, materials science, pharmaceutical and drug chemistry, and other applications^[1].

Following its potentiality, charge density analysis of mineral structures from natural samples is one of the main interests of the Chemical Crystallography Group (GCQ) at the Federal University of Minas Gerais (UFMG) in Brazil. These structures are very diverse and present a large variety of chemical interactions in their crystal structures, and are relevant to geology and materials science. In this sense, we apply quantum crystallographic methods such as the Hansen-Coppens multipolar model (MM)^[2] and Hirshfeld Atom Refinement (HAR)^{[3, 4]} to describe these structures.

Recently, I was awarded the IUCR Best Poster Award at the LACA-ABCR 2025 meeting for my work “Charge Density Analysis of a Zircon (ZrSiO₄) Sample from Alcalino do Itatiaia, Brazil”. In the work, I studied a crystal of the mineral zircon and compared the results from the Isolated Atom Model and MM refinements^[2]. I also presented results from the topological analysis using the Quantum Theory of Atoms in Molecules (QTAIM) by Richard Bader^[5]. We obtained chemically reasonable atomic charges for the atoms from MM and QTAIM. The deformation maps showed the charge transfer from Zr and Si to O atoms. The maps also highlighted the difference between the Si-O and Zr-O bonds. The topological analysis enabled me to characterize the chemical bonds in the system, construct the molecular graph, and identify the critical points of the electron density.

It is really gratifying to get the award, and it shows the relevance of the work and that the topic we research is also interesting to the scientific community. Going further, we aim to expand our studies to other structures and keep applying the quantum crystallography models.

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