The construction of potential energy profiles along a reaction coordinate for the ground and excited electronic states provides the “blueprint” of the reactants chemical activity. Quite often the lowest energy molecular structure originates from the excited electronic states of the atoms and/or fragments composing it. For example, acetylene (HCCH) is formed from the excited 4Σ- electronic state of CH [Can. J. Chem. 82, 684 (2004)], whereas boron uses its 4P(2s12p2) excited state to make HBBH, ArBBAr or B3 [J. Phys. Chem. A 108, 4335 (2004); J. Chem. Phys. 128, 144308 (2008); J. Chem. Phys. 132, 164307 (2010)] . Ozone has been demonstrated to form by 82% from an excited O2 (1Δg) and excited atomic oxygen (1D) [J. Am. Chem. Soc. 136, 2808 (2014)]
Because of the large number of low-lying electronic states of transition metals, the description of the reaction between a transition metal and other small molecules necessitates the case study of several excited electronic states. In the past we examined the reaction of the first row transition metals with oxygen. The numerous potential energy curves of CrO spanning an energy range of 20,000 cm-1 are indicative of the complexity of the small transition metal compounds [J. Phys. Chem. A 114, 8536 (2010)]
To cope with the complex multi-radical nature of these systems, we apply advanced computational methodologies such as multi-reference configuration interaction combined with large basis sets.
The targeted reactions in our group pertain to the modern worldwide energy needs. We are highly interested in the reaction of small transition metal compounds with water and methane. Our ultimate goal is the comprehension of the role of both the transition metals and ligands nature on the catalytic water splitting and C-H activation reactions.
The former reaction produces H2 which is considered a viable replacement of the conventional fossil fuels. The latter can aid at the chemical transformation of the inert hydrocarbons, which are abundant in natural gas. The light absorption involved in the above catalytic cycles entails the investigation of the electronically excited reaction pathways.
The second route of our research journey relates to the excited electronic states of solutes (solvated ionic/molecular systems), especially bearing unpaired electrons (radicals). Multireference quantum chemical calculations combined with polarizable solvent models and/or molecular mechanical representation of the solvent molecules are deemed necessary. Electron transfer between two ions and the electronic states of systems crossing an air/water interface are the two main applications in our group [J. Chem. Theory Comput. 11, 1549 (2015)]
We are finally interested in excited electronic states of weak molecular interactions. An interesting case is the fluorescence effect which involves light absorption.
- A. Papakondylis, E. Miliordos and A. Mavridis, “Carbonyl boron and related systems: An ab initio study of B-X and YBBY (1Σg+), where X = He, Ne, Ar, Kr, CO, CS, N2 and Y = Ar, Kr, CO, CS, N2”, Journal Physical Chemistry A 108, 4335 (2004), DOI: 10.1021/jp031308q.
- E. Miliordos and A. Mavridis, “The electronic structure of vanadium oxide. Neutral and charged species, VO0,±”, Journal of Physical Chemistry A 111, 1953 (2007), DOI: 10.1021/jp067451b.
- E. Miliordos, A. Papakondylis, A. A. Tsekouras and A. Mavridis, “All-electron first principles calculations of the ground and some low-lying excited states of BaI”, Journal Physical Chemistry A 111, 10002 (2007), DOI: 10.1021/jp0745788.
- E. Miliordos and A. Mavridis, “Ab initio investigation of the electronic structure and bonding of BH, BH‾, and HBBH molecules”, Journal of Chemical Physics 128, 144308 (2008), DOI: 10.1063/1.2902284.
- E. Miliordos and A. Mavridis, “Theoretical study of the early 3d-transition metal diatomic oxides and their ions: ScO0,±, TiO0,±, CrO0,±, MnO0,± ”, Klaus Ruedenberg Special Issue (invited), Journal of Physical Chemistry A 114, 8536 (2010), DOI: 10.1021/jp910218u.
- E. Miliordos and A. Mavridis, “An accurate first principles study of the geometric and electronic structure of B2, B2¯, B3, B3¯, and B3H. Ground and excited states”, Journal of Chemical Physics 132, 164307 (2010), DOI: 10.1063/1.3389133.
- E. Miliordos, “Hückel versus Möbius aromaticity: The particle in a cylinder versus a Möbius strip”, Physical Review A 82, 062118 (2010), DOI: 10.1103/PhysRevA.82.062118. Highlighted in Science News issue of January 29, 2011 (page 16), https://www.sciencenews.org/article/twisted-rules-chemistry-explained.
- E. Miliordos and K. L. C. Hunt, “First principles calculations of the electronic and geometrical structures of neutral [Sc,O,H] molecules and the monocations, ScOH0,+ and HScO0,+”, Journal of Physical Chemistry A 115, 4436 (2011), DOI: 10.1021/jp110378d.
- E. Miliordos, “The particle in a Möbius wire and half-integer orbital angular momentum”, Physical Review A 83, 062107 (2011), DOI: 10.1103/PhysRevA.83.062107.
- C. N. Sakellaris, E. Miliordos and A. Mavridis, “First principles study of the ground and excited states of FeO, FeO+, and FeO‾ ”, Journal of Chemical Physics 134, 234308 (2011), DOI: 10.1063/1.3598529.
- E. Miliordos, J. F. Harrison and K. L. C. Hunt, “Ab initio investigation of titanium hydroxide isomers and their cations, TiOH0,+ and HTiO0,+ ”, Journal of Chemical Physics 135, 144111 (2011), DOI: 10.1063/1.3644963.
- X. Li, A. Mandal, E. Miliordos and K. L. C. Hunt, “Interaction-induced dipoles of hydrogen molecules colliding with helium atoms: A new ab initio dipole surface for high-temperature applications”, Journal of Chemical Physics 136, 044320 (2012), DOI: 10.1063/1.3676406.
- E. Miliordos, J. F. Harrison and K. L. C. Hunt, “Ground and excited states of vanadium hydroxide isomers and their cations, VOH0,+ and HVO0,+ ”, Journal of Chemical Physics 138, 114305 (2013), DOI: 10.1063/1.4793744.
- E. Miliordos and J. F. Harrison, “Hirshfeld density partitioning technique: a first application on transition metal compounds, TiO, VO, ScOH”, Journal of Chemical Physics 138, 184305 (2013), DOI: 10.1063/1.4803478.
- E. Miliordos, K. Ruedenberg and S. S. Xantheas, “Unusual inorganic biradicals: A Theoretical Analysis”, Communication to the Editor, Angewandte Chemie International Edition 52, 5736 (2013), DOI: 10.1002/anie.201300654.
- E. Miliordos and S. S. Xantheas, “Efficient procedure for the numerical calculation of harmonic vibrational frequencies based on internal coordinates” Joel M. Bowman Special Issue (invited), Journal of Physical Chemistry A 117, 7019 (2013), DOI: 10.1021/jp3127576.
- E. Miliordos, E. Aprà and S. S. Xantheas, “Optimal geometries and harmonic vibrational frequencies of the global minima of water clusters (H2O)n, n=2-6, and several hexamer local minima at the CCSD(T) level of theory” Journal of Chemical Physics 139, 114302 (2013), DOI: 10.1063/1.4820448.
- E. Miliordos and S. S. Xantheas, “Elucidating the mechanism behind the stabilization of multi-charged metal cations in water: A case study of the electronic states of microhydrated Mg2+, Ca2+ and Al3+”, Hot article for the week Oct 22, 2013 (http://blogs.rsc.org/cp/2013/10/22/this-weeks-hot-articles-11/), Highlighted in NERSC’s web page, June 2014, http://www.nersc.gov/news-publications/news/science-news/2014/thirsty-metals-key-to-longer-battery-lifetimes/. Highlighted in DOE’s Pulse (Science and Technology Highlights from the DOE National Laboratories, #417, 7 July 2014 http://web.ornl.gov/info/news/pulse/no417/story1.shtml. Reported in Science Springs, July 7 2014 http://sciencesprings.wordpress.com/2014/07/07/from-doe-pulse-satisfying-metals-thirst-vital-for-high-capacity-batteries, Communication to the Editor, Physical Chemistry Chemical Physics 16, 6886 (2014), DOI: 10.1039/c3cp53636j. Journal cover.
- E. Miliordos and S. S. Xantheas, “Unimolecular and hydrolysis channels for the detachment of water from microsolvated alkaline earth dication (Mg2+, Ca2+, Sr2+, Ba2+) clusters”, Thom H. Dunning Jr. Special Issue (invited), Theoretical Chemistry Accounts 133, 1450 (2014), DOI: 10.1007/s00214-014-1450-4.
- E. Miliordos and S. S. Xantheas, “On the bonding nature of ozone (O3) and its sulfur-substituted analogues, SO2, OS2, and S3: Correlation between their biradical character and molecular properties” Journal of the American Chemical Society 136, 2808 (2014), DOI: 10.1021/ja410726u.
- E. Miliordos, E. Aprà and S. S. Xantheas, “Benchmark Theoretical Study of the π−π Binding Energy in the Benzene Dimer” Journal of Physical Chemistry A 118, 7568 (2014), DOI: 10.1021/jp5024235.
- N. Sahu, S. R. Gadre, A. Rakshit, P. Bandyopadhyay, E. Miliordos and S. S. Xantheas, “Low energy isomers of (H2O)25 from a hierarchical method based on Monte Carlo temperature basin paving and molecular tailoring approaches benchmarked by MP2 calculations” Journal of Chemical Physics 141, 164304 (2014), DOI: 10.1063/1.4897535.
- J. C. Werhahn, E. Miliordos and S. S. Xantheas, “A new variation of the Buckingham exponential-6 potential with a tunable, singularity-free short-range repulsion and an adjustable long-range attraction” Chemical Physics Letters 619, 153 (2015), DOI: 10.1016/j.cplett.2014.11.051.
- T. Karman, E. Miliordos, K. L. C. Hunt, G. C. Groenenboom and Ad van der Avoird, “Quantum mechanical calculation of the collision-induced absorption spectra of N2–N2 with anisotropic interactions” Journal of Chemical Physics 142, 084306 (2015), DOI: 10.1063/1.4907917.
- E. Miliordos and S. S. Xantheas, “On the validity of the basis set superposition error and complete basis set limit extrapolations for the binding energy of the formic acid dimer”, Journal of Chemical Physics 142, 094311 (2015), DOI: 10.1063/1.4913766.
- E. Miliordos and S. S. Xantheas, “Ground and excited states of the [Fe(H2O)6]2+ and [Fe(H2O)6]3+ clusters: Insight into the electronic structure of the [Fe(H2O)6]2+–[Fe(H2O)6]3+”, J. Chem. Theory Comput. 11, 1549 (2015), DOI: 10.1021/ct501143c.
- E. Miliordos and S. S. Xantheas, “An accurate and efficient computational protocol for obtaining the complete basis set limits of the binding energies of water clusters at the MP2 and CCSD(T) levels of theory: Application to (H2O)m, m = 2-6, 8, 11, 16, and 17”, J. Chem. Phys. 142, 234303 (2015), DOI: 10.1063/1.4922262.
- E. Miliordos and S. S. Xantheas, “The origin of the reactivity of the Criegee intermediate: implications for atmospheric particle growth”, Angew. Chemie Int. Ed. 55, 1015 (2016), DOI: 10.1002/anie.201509685.
- C. T. Wolke, J. A. Fournier, E. Miliordos, S. M. Kathmann, S. S. Xantheas, and M. A. Johnson, “Isotopomer-selective spectra of a single intact H2O molecule in the Cs+(D2O)5H2O isotpologue: Going beyond pattern recognition to harvest the structural information encoded in vibrational spectra”, J. Chem. Phys. 144, 074305 (2016), DOI: 10.1063/1.4941285.
- E. Miliordos, E. Aprà and S. S. Xantheas, “A new, dispersion-driven intermolecular arrangement for the benzene-water octamer complex: Isomers and analysis of their vibrational spectra”, J. Chem. Theory Comput. 12, 4004 (2016), DOI: 10.1021/acs.jctc.6b00668.
- E. Miliordos, S. Caratzoulas and D. G. Vlachos, “A periodic-DFT study of retro-aldol fragmentation of fructose on MoO3”, Appl. Catal. A 530, 75 (2017), DOI: 10.1016/j.apcata.2016.11.021.