• Constrained Density Functional Theory: A Potential-Based Self-Consistency Approach 

      Gonze, Xavier; Seddon, Benjamin; Elliott, James A.; Tantardini, Christian; Shapeev, Alexander V. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-13)
      Chemical reactions, charge transfer reactions, and magnetic materials are notoriously difficult to describe within Kohn−Sham density functional theory, which is strictly a groundstate technique. However, over the last few decades, an approximate method known as constrained density functional theory (cDFT) has been developed to model low-lying excitations linked to charge transfer or spin ...
    • Constrained DFT-based magnetic machine-learning potentials for magnetic alloys: a case study of Fe–Al 

      Tantardini, Christian; Kotykhov, Alexey S.; Gubaev, Konstantin; Hodapp, Max; Shapeev, Alexander V.; Novikov, van S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-13)
      We propose a machine-learning interatomic potential for multi-component magnetic materials. In this potential we consider magnetic moments as degrees of freedom (features) along with atomic positions, atomic types, and lattice vectors. We create a training set with constrained DFT (cDFT) that allows us to calculate energies of confgurations with non-equilibrium (excited) magnetic moments and, ...
    • Crystal Structure Evolution of Fluorine under High Pressure 

      Tantardini, Christian; Jalolov, Faridun N.; Kvashnin, Alexander G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-01)
      Fluorinated compounds in the last decade were applied as photothermo-refractive glasses, high-stress lubricants, and pharmaceutical drugs due to their good mechanical properties and biocompatibility. Although fluorinated materials are largely employed, the possibility of predicting new structures was limited by the impossibility to use density functional theory (DFT) to describe interatomic ...
    • Electronic Properties of Functionalized Diamanes for Field-Emission Displays 

      Tantardini, Christian; Kvashnin, Alexander G.; Azizi, Maryam; Gonze, Xavier; Gatti, Carlo; Altalhi, Tariq; Yakobson, Boris I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)
      Ultrathin diamond films, or diamanes, are promising quasi-2D materials that are characterized by high stiffness, extreme wear resistance, high thermal conductivity, and chemical stability. Surface functionalization of multilayer graphene with different stackings of layers could be an interesting opportunity to induce proper electronic properties into diamanes. Combination of these electronic ...
    • Electronic Properties of Zn<inf>2</inf>V<inf>(1-x)</inf>Nb<inf>x</inf>N<inf>3</inf> Alloys to Model Novel Materials for Light-Emitting Diodes 

      Stratulat, Ana-Maria; Tantardini, Christian; Azizi, Maryam; Altalhi, Tariq; Levchenko, Sergey V.; Yakobson, Boris I. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-04)
      We propose the Zn<sub>2</sub>V(<sub>1–x</sub>)Nb<sub>x</sub>N<sub>3</sub> alloy as a new promising material for optoelectronic applications, in particular for light-emitting diodes (LEDs). We perform accurate electronic-structure calculations of the alloy for several concentrations x using density-functional theory with meta-GGA exchange–correlation functional TB09. The band gap is found to vary ...
    • Full Breit Hamiltonian in the Multiwavelets Framework 

      Tantardini, Christian; Remigio, Roberto Di; Bjørgve, Magnar; Jensen, Stig Rune; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-01)
      New techniques in core–electron spectroscopy are necessary to resolve the structures of oxides of f-elements and other strongly correlated materials that are present only as powders and not as single crystals. Thus, accurate quantum chemical methods must be developed to calculate core spectroscopic properties in such materials. In this contribution, we present an important development in this ...
    • GIPAW Pseudopotentials of d Elements for Solid-State NMR 

      Tantardini, Christian; Kvashnin, Alexander G.; Ceresoli, Davide (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-06)
      Computational methods are increasingly used to support interpreting, assigning and predicting the solid-state nuclear resonance magnetic spectra of materials. Currently, density functional theory is seen to achieve a good balance between efficiency and accuracy in solid-state chemistry. To be specific, density functional theory allows the assignment of signals in nuclear resonance magnetic spectra ...
    • Scalar Relativistic Effects with Multiwavelets: Implementation and Benchmark 

      Brakestad, Anders; Jensen, Stig Rune; Tantardini, Christian; Pitteloud, Quentin Gregoire; Wind, Peter Ariaan; Užulis, Jānis; Gulans, Andris; Hopmann, Kathrin Helen; Frediani, Luca (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-05)
      The importance of relativistic effects in quantum chemistry is widely recognized, not only for heavier elements but throughout the periodic table. At the same time, relativistic effects are strongest in the nuclear region, where the description of electrons through a linear combination of atomic orbitals becomes more challenging. Furthermore, the choice of basis sets for heavier elements is ...
    • Translucency and Color Stability of a Simplified Shade Nanohybrid Composite after Ultrasonic Scaling and Air-Powder Polishing 

      Babina, Ksenia; Polyakova, Maria; Sokhova, Inna; Doroshina, Vladlena; Zaytsev, Alexandr; Nikonova, Elena E.; Budylin, Gleb S.; Shirshin, Evgeny A.; Tantardini, Christian; Novozhilova, Nina (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-15)
      We aimed to assess the influence of professional dental prophylaxis on the translucency and color stability of a novel simplified shade nanohybrid composite material. Sixty composite disks (5 mm in diameter and 2 mm thick) of light (n = 30) and dark (n = 30) shades were prepared. The specimens were randomly divided into the following three groups (n = 10) according to the prophylaxis procedure ...
    • Ultrafast Polarization Switching in BaTiO<inf>3</inf> Nanomaterials: Combined Density Functional Theory and Coupled Oscillator Study 

      Zhilyaev, Petr; Brekhov, Kirill; Mishina, Elena; Tantardini, Christian (Journal article; Tidsskriftartikkel; Peer reviewed, 2024-01-17)
      The challenge of achieving ultrafast switching of electric polarization in ferroelectric materials remains unsolved as there is no experimental evidence of such switching to date. In this study, we developed an enhanced model that describes switching within a two-dimensional space of generalized coordinates at THz pulses. Our findings indicate that stable switching in barium titanate cannot be ...