{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T09:10:16Z","timestamp":1790327416515,"version":"4.1.0"},"reference-count":49,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T00:00:00Z","timestamp":1790294400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005375","name":"Latvian Council of Science","doi-asserted-by":"publisher","award":["LZP-2023\/1-0063"],"award-info":[{"award-number":["LZP-2023\/1-0063"]}],"id":[{"id":"10.13039\/501100005375","id-type":"DOI","asserted-by":"publisher"}]},{"award":["LZP-2023\/1-0063"],"award-info":[{"award-number":["LZP-2023\/1-0063"]}],"id":[{"id":"https:\/\/ror.org\/02ar66p97","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Nanomaterials"],"abstract":"<jats:p>In this study, first-principles simulations of inverse spinel Mg2TiO4 (MTO) and MTO:Mn4+ on the base of the tetragonal phase were performed within the linear combination of atomic orbitals (LCAO) approximation of density functional theory (DFT), as implemented in CRYSTAL23 computer code. The effect of Mn doping on the MTO band gap structure was studied for the first time. Lattice relaxation around Mn4+ ions upon substitution was considered. Two possible spin configurations of the Mn4+ ion (3d3) in MTO:Mn4+ (total spin of system S = 3\/2 and 1\/2) were considered in the framework of the unrestricted (open shell) DFT-LCAO calculations. The structural, electronic, vibrational, dielectric and elastic properties of materials were investigated, compared and discussed. It has been shown that dopant atoms create new defect states within the band gap and modify the conduction band and the valence band, which is one of the most important results in the present study. The effect of isotopic substitution on the vibrational properties was analyzed. Based on the calculated elastic moduli, the Debye temperature for MTO was estimated. This study provides a basis for the assessment of the optical and luminescent properties of the doped material and its use in LED applications.<\/jats:p>","DOI":"10.3390\/nano16191213","type":"journal-article","created":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T08:09:02Z","timestamp":1790323742000},"page":"1213","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["First-Principles Calculations of Structural, Electronic, Optical, Vibrational, Dielectric, and Elastic Properties of Tetragonal Mg2TiO4 and Mg2TiO4:Mn4+"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4030-6157","authenticated-orcid":false,"given":"Leonid L.","family":"Rusevich","sequence":"first","affiliation":[{"name":"Institute of Solid State Physics, University of Latvia, Kengaraga Street 8, LV-1063 Riga, Latvia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8122-6276","authenticated-orcid":false,"given":"Eugene A.","family":"Kotomin","sequence":"additional","affiliation":[{"name":"Institute of Solid State Physics, University of Latvia, Kengaraga Street 8, LV-1063 Riga, Latvia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4750-5359","authenticated-orcid":false,"given":"Miroslav D.","family":"Drami\u0107anin","sequence":"additional","affiliation":[{"name":"Centre of Excellence for Photoconversion, Vin\u010da Institute of Nuclear Sciences\u2014National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9725-6173","authenticated-orcid":false,"given":"Alok M.","family":"Srivastava","sequence":"additional","affiliation":[{"name":"Current Chemicals Inc., 1099 Ivanhoe Road, Cleveland, OH 44110, USA"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2841-2763","authenticated-orcid":false,"given":"Mikhail G.","family":"Brik","sequence":"additional","affiliation":[{"name":"Institute of Solid State Physics, University of Latvia, Kengaraga Street 8, LV-1063 Riga, Latvia"},{"name":"Centre of Excellence for Photoconversion, Vin\u010da Institute of Nuclear Sciences\u2014National Institute of the Republic of Serbia, University of Belgrade, 11000 Belgrade, Serbia"},{"name":"Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411 Tartu, Estonia"},{"name":"School of Integrated Circuits, Chongqing University of Posts and Telecommunications, Chongqing 400065, China"},{"name":"Academy of Romanian Scientists, 3 Ilfov, 050044 Bucharest, Romania"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,25]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2652","DOI":"10.1039\/C8TC00251G","article-title":"Mn2+ and Mn4+ red phosphors: Synthesis, luminescence and applications in WLEDs. A review","volume":"6","author":"Zhou","year":"2018","journal-title":"J. Mater. Chem. C"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"016001","DOI":"10.1149\/2.0022001JSS","article-title":"Review-Mn4+-Activated Red and Deep Red-Emitting Phosphors","volume":"9","author":"Adachi","year":"2020","journal-title":"ECS J. Solid State Sci. Technol."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"263","DOI":"10.1016\/j.jlumin.2018.05.053","article-title":"Photoluminescence properties of Mn4+-activated oxide phosphors for use in white-LED applications: A review","volume":"202","author":"Adachi","year":"2018","journal-title":"J. Lumin."},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Xie, Y.P., Tian, T., Mao, C.L., Wang, Z.Y., Shi, J.J., Yang, L., and Wang, C.C. (2023). Recent Research Progress of Mn4+-Doped A2MF6 (A = Li, Na, K, Cs, or Rb; M = Si, Ti, Ge, or Sn) Red Phosphors Based on a Core-Shell Structure. Nanomaterials, 13.","DOI":"10.3390\/nano13030599"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"114073","DOI":"10.1016\/j.materresbull.2026.114073","article-title":"Recent progress of fluoride phosphors doped with Mn4+ and Cr3+: A review","volume":"200","author":"Zhou","year":"2026","journal-title":"Mater. Res. Bull."},{"key":"ref_6","unstructured":"Radkov, E.V., Grigorov, L.S., Setlur, A.A., and Srivastava, A.M. (2009). Red Line Emitting Phosphor Materials for Use in LED Applications. (US patent US7497973B2)."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"118167","DOI":"10.1016\/j.jlumin.2021.118167","article-title":"Recent prospects on phosphor-converted LEDs for lighting, displays, phototherapy, and indoor farming","volume":"237","author":"Bispo","year":"2021","journal-title":"J. Lumin."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"69","DOI":"10.1016\/j.jlumin.2011.08.047","article-title":"On the optical properties of the Mn4+ ion in solids","volume":"133","author":"Brik","year":"2013","journal-title":"J. Lumin."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"R39","DOI":"10.1149\/2.0031503jss","article-title":"Influence of Covalency on the Mn4+ 2Eg \u2192 4A2g Emission Energy in Crystals","volume":"4","author":"Brik","year":"2015","journal-title":"ECS J. Solid State Sci. Technol."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Rusevich, L.L., Brik, M.G., Gryaznov, D., Srivastava, A.M., Chervyakov, I., Zvejnieks, G., Bocharov, D., and Kotomin, E.A. (2024). First-Principles Linear Combination of Atomic Orbitals Calculations of K2SiF6 Crystal: Structural, Electronic, Elastic, Vibrational and Dielectric Properties. Materials, 17.","DOI":"10.3390\/ma17194865"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Rusevich, L.L., Brik, M.G., Gryaznov, D., Srivastava, A.M., Chervyakov, I.D., Zvejnieks, G., Bocharov, D., and Kotomin, E.A. (2025). A Comparative Study of A2SiF6 (A = Cs, K) Phosphor Host Matrices: Linear Combination of Atomic Orbital Hybrid Density Functional Theory Calculations. Materials, 18.","DOI":"10.3390\/ma18092025"},{"key":"ref_12","unstructured":"Chervyakov, I., Rusevich, L., Bocharov, D., Brik, M., and Kotomin, E. (2026, January 15\u201318). Computational study of the structural, electronic, vibrational and elastic properties of Na2SiF6 and Na2SiF6:Mn4+ phosphors. Proceedings of the Functional Materials and Nanotechnologies FMNT 2026, Riga, Latvia."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"542","DOI":"10.1107\/S010876818900786X","article-title":"Structure refinements of Mg2TiO4, MgTiO3 and MgTi2O5 by time-of-flight neutron powder diffraction","volume":"B45","author":"Wechsler","year":"1989","journal-title":"Acta Cryst."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"885","DOI":"10.2138\/am-1995-9-1003","article-title":"Study of the cubic to tetragonal transition in Mg2TiO4 and Zn2TiO4 spinels by 17O MAS NMR and Rietveld refinement of X-ray diffraction data","volume":"80","author":"Millard","year":"1995","journal-title":"Am. Mineral."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1363","DOI":"10.2138\/am.2008.2896","article-title":"A computational study of order-disorder phenomena in Mg2TiO4 spinel (qandilite)","volume":"93","author":"Palin","year":"2008","journal-title":"Amer. Mineral."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"054114","DOI":"10.1103\/PhysRevB.81.054114","article-title":"Classification of spinel structures based on first-principles cluster expansion analysis","volume":"81","author":"Seko","year":"2010","journal-title":"Phys. Rev. B"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"9","DOI":"10.1149\/05041.0009ecst","article-title":"Investigation of Ion Dependence of Electronic Structure for 3d3 Ions in Mg2TiO4 Based on First-Principles Calculations","volume":"50","author":"Novita","year":"2013","journal-title":"ECS Trans."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"272","DOI":"10.3103\/S0027134916030140","article-title":"First-Principles Study of the Structural, Elastic, Mechanical, Electronic, and Optical Properties of Cubic Mg2TiO4","volume":"71","author":"Zeng","year":"2016","journal-title":"Moscow. Univ. Phys. Bull."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"210","DOI":"10.1007\/s00894-019-4098-0","article-title":"First principles investigations of the structural, elastic, vibrational and thermodynamic properties of TiMg2O4 oxide spinels: Cubic and tetragonal phases","volume":"25","author":"Kushwaha","year":"2019","journal-title":"J. Mol. Model."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"424","DOI":"10.15407\/spqeo28.04.424","article-title":"Distribution of Mg and Ti atoms over octahedral sites and physical properties of Mg2TiO4","volume":"28","author":"Kashirina","year":"2025","journal-title":"Semicond. Phys. Quantum Electron. Optoelectron."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"6214","DOI":"10.1007\/s11664-016-4846-1","article-title":"Thin-Film Photoluminescent Properties and the Atomistic Model of Mg2TiO4 as a Non-rare Earth Matrix Material for Red-Emitting Phosphor","volume":"45","author":"Huang","year":"2016","journal-title":"J. Electron. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1769","DOI":"10.1021\/acs.chemmater.8b00149","article-title":"Ab Initio-Aided Sensitizer Design for Mn4+-Activated Mg2TiO4 as an Ultrabright Fluoride-Free Red-Emitting Phosphor","volume":"30","author":"Huang","year":"2018","journal-title":"Chem. Mater."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"15687","DOI":"10.1021\/acs.jpcc.1c04293","article-title":"Tuning the Mn4+ Coordination Environment in Mg2TiO4 through a Codoping Strategy for Enhancing Luminescence Performance","volume":"125","author":"Han","year":"2021","journal-title":"J. Phys. Chem. C"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"724","DOI":"10.1021\/jp5095646","article-title":"Deep-Red Emitting Mn4+ Doped Mg2TiO4 Nanoparticles","volume":"119","author":"Brik","year":"2015","journal-title":"J. Phys. Chem. C"},{"key":"ref_25","unstructured":"Dovesi, R., Saunders, V.R., Roetti, C., Orlando, R., Zicovich-Wilson, C.M., Pascale, F., Civalleri, B., Doll, K., Harrison, N.M., and Bush, I.J. (2022). CRYSTAL23 User\u2019s Manual, University of Torino."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"6891","DOI":"10.1021\/acs.jctc.2c00958","article-title":"CRYSTAL23: A program for computational solid state physics and chemistry","volume":"19","author":"Erba","year":"2023","journal-title":"J. Chem. Theory Comput."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"2364","DOI":"10.1002\/jcc.26013","article-title":"BSSE-correction scheme for consistent gaussian basis sets of double- and triple-zeta valence with polarization quality for solid-state calculations","volume":"40","author":"Oliveira","year":"2019","journal-title":"J. Comput. Chem."},{"key":"ref_28","unstructured":"(2026, September 07). CRYSTAL Basis Sets Library. Available online: https:\/\/www.crystal.unito.it\/basis_sets.html."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"165107","DOI":"10.1103\/PhysRevB.77.165107","article-title":"Hybrid exchange-correlation functional for accurate prediction of the electronic and structural properties of ferroelectric oxides","volume":"77","author":"Bilc","year":"2008","journal-title":"Phys. Rev. B"},{"key":"ref_30","unstructured":"Decius, J.C., and Hexter, R.M. (1977). Molecular Vibrations in Crystals, McGraw-Hill."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"385","DOI":"10.1063\/1.455480","article-title":"Ab initio analytic polarizability, first and second hyperpolarizabilities of large conjugated organic molecules: Applications to polyenes C4H6 to C22H24","volume":"89","author":"Hurst","year":"1988","journal-title":"J. Chem. Phys."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1294","DOI":"10.1063\/1.481907","article-title":"Extension of the Genkin and Mednis treatment for dynamic polarizabilities and hyperpolarizabilities of infinite periodic systems. I. Coupled perturbed Hartree\u2013Fock theory","volume":"113","author":"Kirtman","year":"2000","journal-title":"J. Chem. Phys."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"109399","DOI":"10.1016\/j.diamond.2022.109399","article-title":"The vibrational and dielectric properties of diamond with N impurities: First principles study","volume":"130","author":"Rusevich","year":"2022","journal-title":"Diam. Relat. Mater."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"115222","DOI":"10.1016\/j.optmat.2024.115222","article-title":"The electronic, vibrational and dielectric properties of diamond crystals with neutral vacancies: First principles study","volume":"150","author":"Rusevich","year":"2024","journal-title":"Opt. Mater."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"8336","DOI":"10.1021\/acs.jpcc.8b08902","article-title":"Calculation of the infrared intensity of crystalline systems. A comparison of three strategies based on Berry phase, Wannier function, and coupled-perturbed Kohn-Sham methods","volume":"123","author":"Dovesi","year":"2019","journal-title":"J. Phys. Chem. C"},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"164101","DOI":"10.1063\/1.4824442","article-title":"Ab initio analytical Raman intensities for periodic systems through a coupled perturbed Hartree-Fock\/Kohn-Sham method in an atomic orbital basis","volume":"139","author":"Maschio","year":"2013","journal-title":"I. Theory. J. Chem. Phys."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"164102","DOI":"10.1063\/1.4824443","article-title":"Ab initio analytical Raman intensities for periodic systems through a coupled perturbed Hartree-Fock\/Kohn-Sham method in an atomic orbital basis. II. Validation and comparison with experiments","volume":"139","author":"Maschio","year":"2013","journal-title":"J. Chem. Phys."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"1272","DOI":"10.1107\/S0021889811038970","article-title":"VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data","volume":"44","author":"Momma","year":"2011","journal-title":"J. Appl. Crystallogr."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"751","DOI":"10.1107\/S0567739476001551","article-title":"Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides","volume":"A32","author":"Shannon","year":"1976","journal-title":"Acta Cryst."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"2087","DOI":"10.1038\/s41467-021-22429-0","article-title":"Thermochemical electronegativities of the elements","volume":"12","author":"Tantardini","year":"2021","journal-title":"Nat. Commun."},{"key":"ref_41","unstructured":"Brown, I.D. (1981). Structure and Bonding in Crystals, Academic Press."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"244","DOI":"10.1107\/S0108768185002063","article-title":"Bond-Valence Parameters Obtained from a Systematic Analysis of the Inorganic Crystal Structure Database","volume":"41","author":"Brown","year":"1985","journal-title":"Acta Crystallogr."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"40152","DOI":"10.1039\/C7RA06382B","article-title":"Characterization of blue-excited yellow phosphor (Y,Ca)6+x\/3Si11(N,O)21:Ce by the bond valence sum model","volume":"7","author":"Seto","year":"2017","journal-title":"RSC Adv."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"6455","DOI":"10.1111\/jace.17997","article-title":"Theoretical study on composition-dependent properties of ZnO\u00b7nAl2O3 spinels. Part II: Mechanical and thermophysical","volume":"104","author":"Xu","year":"2021","journal-title":"J. Am. Ceram. Soc."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"196","DOI":"10.1016\/j.surfcoat.2013.01.048","article-title":"Optical properties of ambient temperature grown nanocrystalline Mg2TiO4 thin films","volume":"221","author":"Bhuyan","year":"2013","journal-title":"Surf. Coat. Technol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"224104","DOI":"10.1103\/PhysRevB.90.224104","article-title":"Necessary and sufficient elastic stability conditions in various crystal systems","volume":"90","author":"Mouhat","year":"2014","journal-title":"Phys. Rev. B"},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"349","DOI":"10.1088\/0370-1298\/65\/5\/307","article-title":"The elastic behaviour of a crystalline aggregate","volume":"65","author":"Hill","year":"1952","journal-title":"Proc. Phys. Soc. A"},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"823","DOI":"10.1080\/14786440808520496","article-title":"XCII. Relations between the elastic moduli and the plastic properties of polycrystalline pure metals","volume":"45","author":"Pugh","year":"1954","journal-title":"Philos. Mag."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"909","DOI":"10.1016\/0022-3697(63)90067-2","article-title":"A simplified method for calculating the Debye temperature from elastic constants","volume":"24","author":"Anderson","year":"1963","journal-title":"J. Phys. Chem. Solids"}],"container-title":["Nanomaterials"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2079-4991\/16\/19\/1213\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,25]],"date-time":"2026-09-25T08:36:29Z","timestamp":1790325389000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2079-4991\/16\/19\/1213"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,25]]},"references-count":49,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["nano16191213"],"URL":"https:\/\/doi.org\/10.3390\/nano16191213","relation":{},"ISSN":["2079-4991"],"issn-type":[{"value":"2079-4991","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,25]]}}}