The Role of Quantum Chemistry in Complex Molecular ‎Systems

  • Authors

    https://doi.org/10.14419/z3kbt082

    Received date: November 21, 2025

    Accepted date: January 9, 2026

    Published date: January 16, 2026

  • Density Functional Theory; Transition-Metal Chemistry; Multireference Methods; Bond ‎Dissociation; Non-Adiabatic Phenomena; Magnetic Coupling; and Excited States

  • Abstract

    Quantum chemistry provides a rigorous theoretical framework for describing molecular ‎behavior at the electronic scale, offering capabilities that fundamentally surpass the ‎explanatory and predictive limits of classical and semi-empirical models. Unlike classical ‎approaches, which treat electrons implicitly or rely on parameterized interactions, quantum ‎chemical methods explicitly resolve electronic structure, enabling reliable predictions of ‎molecular geometries, reaction energetics, and electronic reactivity in chemically complex ‎systems. This study critically examines the performance and limitations of quantum chemistry ‎across four particularly challenging domains: transition-metal complexes, bond dissociation ‎phenomena, near-degenerate electronic states, and magnetic or electronically excited systems. ‎While Density Functional Theory (DFT) offers an efficient balance between accuracy and ‎computational cost, its reliability can degrade in systems with strong electron correlation, ‎necessitating the use of multi-reference and wave function-based methods. Through this ‎comparative analysis, the study demonstrates how advances in quantum chemical theory and ‎computation have significantly improved predictive accuracy, deepened understanding of ‎chemical bonding and reactivity, and enabled practical progress in catalysis, spectroscopy, ‎materials science, and photo-physics while also highlighting the methodological trade-offs ‎that continue to define the field‎.

  • References

    1. Field, M. J., Bash, P. A., & Karplus, M. (1990). A combined quantum mechanical and molecular mechanical potential for molecular dynamics simu-lations. Journal of Computational Chemistry, 11, 700–733. https://doi.org/10.1002/jcc.540110605.
    2. Friesner, R. A., & Guallar, V. (2005). Ab initio quantum chemical and mixed quantum mechanics/molecular mechanics (QM/MM) methods for studying enzymatic catalysis. Annual Review of Physical Chemistry, 56, 389–427. https://doi.org/10.1146/annurev.physchem.55.091602.094410.
    3. Raghavachari, K., & Anderson, J. B. (1996). Electron correlation effects in molecules. The Journal of Physical Chemistry, 100, 12960–12973. https://doi.org/10.1021/jp953749i.
    4. Ramachandran, K. I., Deepa, G., & Namboori, K. (2008). Computational Chemistry and Molecular Modelling: Principles and Applications. Berlin: Springer.
    5. Senn, H. M., & Thiel, W. (2007). QM/MM studies of enzymes. Current Opinion in Chemical Biology, 11, 182–187. https://doi.org/10.1016/j.cbpa.2007.01.684.
    6. Senn, H. M., & Thiel, W. (2009). QM/MM methods for biomolecular systems. Angewandte Chemie International Edition, 48, 1198–1229. https://doi.org/10.1002/anie.200802019.
    7. Staib, A., & Borgis, D. (1995). Molecular dynamics simulation of an excess charge in water using mobile Gaussian orbitals. The Journal of Chemi-cal Physics, 103, 2642–2655. https://doi.org/10.1063/1.470524.
    8. Frontiers in Chemistry Editorial Office. (2018). Frontiers in Chemistry, 6, Article 357. https://www.frontiersin.org/articles/10.3389/fchem.2018.00357.
    9. Stefanovich, E. V., & Truong, T. N. (1996). Embedded density functional approach for calculations of adsorption on ionic crystals. The Journal of Chemical Physics, 104, 2946–2955. https://doi.org/10.1063/1.471115.
    10. Timmins, A., Saint-André, M., & de Visser, S. P. (2017). Understanding how prolyl-4-hydroxylase structure steers a ferryl oxidant toward scission of a strong C–H bond. Journal of the American Chemical Society, 139, 9855–9866. https://doi.org/10.1021/jacs.7b02839.
    11. Tuñón, I., Martins-Costa, M. T. C., Millot, C., & Ruiz-López, M. F. (1995). Coupled density functional/molecular mechanics Monte Carlo simula-tions of ions in water: The bromide ion. Chemical Physics Letters, 241, 450–456. https://doi.org/10.1016/0009-2614(95)00615-B.
    12. Tuñón, I., Martins-Costa, M. T. C., Millot, C., Ruiz-López, M. F., & Rivail, J. L. (1996). A coupled density functional–molecular mechanics Monte Carlo simulation method: The water molecule in liquid water. Journal of Computational Chemistry, 17, 19–29. https://doi.org/10.1002/(SICI)1096-987X(19960115)17:1<19::AID-JCC2>3.0.CO;2-3.
    13. van der Kamp, M. W., & Mulholland, A. J. (2013). Combined quantum mechanics/molecular mechanics (QM/MM) methods in computational en-zymology. Biochemistry, 52, 2708–2728. https://doi.org/10.1021/bi400215w.
    14. van Duin, A. C. T., Dasgupta, S., Lorant, F., & Goddard, W. A. (2001). ReaxFF: A reactive force field for hydrocarbons. The Journal of Physical Chemistry A, 105, 9396–9409. https://doi.org/10.1021/jp004368u.
    15. Gao, J. (1993). Potential of mean force for the isomerization of DMF in aqueous solution: A Monte Carlo QM/MM simulation study. Journal of the American Chemical Society, 115, 2930–2935. https://doi.org/10.1021/ja00060a047.
    16. Gao, J. (1996). Hybrid quantum and molecular mechanical simulations: An alternative avenue to solvent effects in organic chemistry. Accounts of Chemical Research, 29, 298–305. https://doi.org/10.1021/ar950140r.
    17. Golze, D., Hutter, J., & Iannuzzi, M. (2015). Wetting of water on hexagonal boron nitride@Rh(111): A QM/MM model based on atomic charges derived for nanostructured substrates. Physical Chemistry Chemical Physics, 17, 14307–14316. https://doi.org/10.1039/C4CP04638B.
    18. Golze, D., Iannuzzi, M., Nguyen, M., Passerone, D., & Hutter, J. (2013). Simulation of adsorption processes at metallic interfaces: An image-charge-augmented QM/MM approach. Journal of Chemical Theory and Computation, 9, 5086–5097. https://doi.org/10.1021/ct400698y.
    19. Gonis, A., & Garland, J. W. (1977). Multishell method: Exact treatment of a cluster in an effective medium. Physical Review B, 16, 2424–2434. https://doi.org/10.1103/PhysRevB.16.2424.
    20. Hartke, B., & Grimme, S. (2010). Reactive force fields made simple. Physical Chemistry Chemical Physics, 12, 16715–16718. https://doi.org/10.1039/C5CP02580J.
    21. Herschend, B. W., Baudin, M., & Hermansson, K. (2004). A combined molecular dynamics–quantum mechanics method for investigation of dy-namic effects on local surface structures. The Journal of Chemical Physics, 120, 4939–4948. https://doi.org/10.1063/1.1635802.
    22. Hofer, T. S. (2014). Perspectives for hybrid ab initio/molecular mechanical simulations of solutions. Pure and Applied Chemistry, 86, 105–117. https://doi.org/10.1515/pac-2014-5019.
    23. Hofer, T. S., Hitzenberger, M., & Randolf, B. R. (2012). Combining a dissociative water model with a hybrid QM/MM approach. Journal of Chem-ical Theory and Computation, 8, 3586–3595. https://doi.org/10.1021/ct300062k.
    24. Hofer, T. S., Rode, B. M., Pribil, A. B., & Randolf, B. R. (2010). Simulations of liquids and solutions based on quantum mechanical forces. Ad-vances in Inorganic Chemistry, 62, 143–175. https://doi.org/10.1016/S0898-8838(10)62004-1.
    25. Hofer, T. S., &Tirler, A. O. (2015). Combining 2D-periodic quantum chemistry with molecular force fields. Journal of Chemical Theory and Com-putation, 11, 5873–5887. https://doi.org/10.1021/acs.jctc.5b00548.
    26. Hofer, T. S., Weiss, A. K. H., Randolf, B. R., & Rode, B. M. (2011). Hydration of highly charged ions. Chemical Physics Letters, 512, 139–144. https://doi.org/10.1016/j.cplett.2011.05.060.
    27. Atkins, P., & Friedman, R. (2021). Molecular Quantum Mechanics (6th ed.). Oxford: Oxford University Press.
    28. Mangaud, E., Jaouadi, A., Chin, A., et al. (2023). Survey of the hierarchical equations of motion in tensor-train format for non-Markovian quantum dynamics. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00919-0.
    29. Dupuy, L., &Scribano, Y. (2023). Coping with the node problem in resonant scattering simulations using quantum trajectories. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00924-3.
    30. Bindech, O., & Marquardt, R. (2023). Mean square displacement of a free quantum particle. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00920-7.
    31. Panadés-Barrueta, R. L., Nadoveza, N., Gatti, F., & Peláez, D. (2023). On the sum-of-products to product-of-sums transformation. European Phys-ical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00928-z.
    32. Kechoindi, S., Ben Yaghlane, S., Terzi, N., Palaudoux, J., &Hochlaf, M. (2023). Characterization and photochemistry of XCO₂ radicals. European Physical Journal Special Topics.https://doi.org/10.1140/epjs/s11734-023-00918-1.
    33. Pereira, A., Knapik, J., Chen, A., et al. (2023). Quantum molecular dynamics simulations of photoisomerization. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00923-4.
    34. Freixas-Lemus, V. M., Martínez-Mesa, A., & Uranga-Piña, L. (2023). Quasi-classical trajectory study of F + HCl reactive scattering. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00945-y.
    35. Lara-Moreno, M., & Stoecklin, T. (2023). Quantum study of the radiative association of Cl⁻ + H₂ and Cl⁻ + D₂. European Physical Journal Special Topics. https://doi.org/10.1140/epjs/s11734-023-00944-z.

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  • How to Cite

    Krishna, R. H. . (2026). The Role of Quantum Chemistry in Complex Molecular ‎Systems. International Journal of Scientific World, 12(1), 1-8. https://doi.org/10.14419/z3kbt082