arXiv subjects

Christian Tantardini

Publications and source records attributed to Christian Tantardini.

At least 19 recordsLinked to original sources

arXiv2026

Statistical admissibility and long-wavelength structural convergence determine representative support in granular materials

Representative elementary areas and volumes provide the scale bridge between resolved granular microstructure and continuum-scale material properties, yet they are still commonly selected from the apparent stabilization of a single scalar observable. Such plateaus can be false indicators of representativeness when statistically incompatible regions are averaged together or when long-wavelength structural correlations remain unresolved. We introduce a general representative-support framework for granular materials based on three sequential requirements: statistical admissibility of the sampled domain, persistent convergence of the apparent field mean and the low-wavenumber covariance spectrum, and validation against independent effective properties. The concept is tested on seven large-area backscattered-electron images of Arabian dune sands and mineral-resolved QEMSCAN maps. The structure-only criterion identifies a representative elementary area of $1536$ pixels, corresponding to approximately $2.01~\mathrm{mm}$. Without property-specific fitting or recalibration, the same physical scale transferred to the QEMSCAN grid $(\approx 2.04~\mathrm{mm})$ coincides with the onset of weak size dependence in apparent thermal conductivity, elastic stiffness, and directional Young's moduli. Thus, the representative scale inferred from long-wavelength granular organization independently predicts the convergence of distinct constitutive responses. The results show that representative support should be assigned only after both statistical compatibility and long-range structural convergence have been established. Although demonstrated here on two-dimensional dune-sand sections, the criterion is formulated for granular materials generally and has a direct mathematical extension to three-dimensional voxelized volumes.

cond-mat.mtrl-sci↗

arXiv2026

Kubo-Martin-Schwinger-Gated Imaginary-Time Reconstruction of Time-Resolved Electronic Circular Dichroism in Organic Excitonic Aggregates

Time-resolved electronic circular dichroism (TR-ECD) and time-resolved circular dichroism (TRCD) probe chiral exciton dynamics prepared by an ultrafast pump and interrogated by a weak circular probe. The measured signal is a causal mixed electric--magnetic response, whereas imaginary-time methods require a sufficiently stationary reference. Here, we introduce a Kubo--Martin--Schwinger-gated criterion that determines, at each pump--probe delay, whether the selected TRCD-like response can be represented by a conditional one-exciton Gibbs ensemble or requires explicit real-time or Keldysh dynamics. The diagnostic combines a state-level distance from the conditional reference with an integrated spectral distance for the reciprocal E1--M1 response. We apply the protocol to three literature-constrained Frenkel-exciton models: a Ress-type squaraine-polymer squeezed helix, a cisoid indolenine squaraine B hexamer, and a helical perylene-bisimide stack. The results show that early nonthermal states are non-admissible, whereas intramanifold population relaxation and the decay of coherence memory can open a Matsubara-admissible delay window before complete excited-state recovery. The resulting gate identifies when imaginary-time methods can be used without imposing a stationary description on a genuinely nonequilibrium chiroptical response.

cond-mat.other↗

arXiv2026

A Nonhomogeneous Porous-Medium Equation for Field Scale CO$_2$ Plume Spreading

We derive a nonlinear diffusion model for field scale CO$_2$ plume spreading from a Global Buckley--Leverett component balance. The reduced variable $u$ is the vertically averaged mobile gas phase CO$_2$ content normalized by its maximum column value; under vertical segregation, $u=h/H$, where $h$ is plume thickness and $H$ is aquifer thickness. The resulting equation is a nonhomogeneous porous medium type equation in which nonlinear lateral spreading is coupled to source/sink terms for injection, dissolution, mineral fixation, and retention. Using the nonlinear diffusivity $D_u(u)\simeq D_0u^{1-q}$, we analyze Barenblatt-type profiles with prescribed mobile mass and a capped plume constrained by $0\le u\le1$. The capped solution contains a ful-thickness core of radius $a(t)$ and a compact plume edge $R(t)$. Constant net mobile injection can sustain the core and gives square-root growth of $R(t)$, whereas shut-in or weak mobile addition causes the core to shrink and disappear. We compare these regimes with equivalent radii from time lapse seismic plume maps at Sleipner, Aquistore, and Weyburn--Midale. The data distinguish injection controlled growth, delayed layer filling, and tail dominated redistribution, but do not determine a unique nonlinear exponent. The model provides an analytical reference for interpreting plume footprint evolution while separating cumulative injected CO$_2$ from mobile gas phase CO$_2$.

physics.flu-dyn↗

arXiv2026

A conservative finite-volume Buckley--Leverett solver with bounded-interval multiwavelet state analysis

We develop a conservative finite-volume Buckley--Leverett solver equipped with a bounded-interval multiwavelet state-analysis layer. Because non-capillary Buckley--Leverett transport is a nonlinear hyperbolic conservation law with entropy-admissible shocks, the saturation equation is advanced by a conservative finite-volume method with monotone numerical fluxes. The accepted finite-volume state is then embedded in a bounded-domain multiwavelet hierarchy, reconstructed back to cell averages, and used for multiresolution diagnostics. The formal transport accuracy is therefore governed by the underlying finite-volume discretization, while the multiwavelet layer is used for representation, compression, and front-localization diagnostics. Its purpose is instead to quantify whether the deterministic physical-space saturation state can be represented faithfully, compressed in a controlled manner, and used to identify dynamically active front regions. Validation against reference Buckley--Leverett profiles for a Berea benchmark shows accurate saturation histories, spatial profiles, front-position diagnostics, and mass balance. The multiwavelet reconstruction tracks the internal finite-volume state with essentially exact fidelity. Additional thresholding tests show that a substantial fraction of detail coefficients can be discarded while maintaining small reconstruction errors and negligible global mass defect, and fine-level detail activity localizes the moving displacement front. The resulting formulation provides a conservative and reproducible first stage toward future transport-active adaptive multiwavelet solvers for porous-media flow.

math.NA↗

arXiv2026

Four-component relativistic calculations in a multiwavelet basis with improved convergence

We revive an approach to solve the Dirac equation originally proposed by Kutzelnigg which makes use of the squared Dirac operator $\hat{\mathfrak{D}}^{2}$. This approach holds the promise to avoid the negative energy solution because the negative energy spectrum is now ``folded" on the positive energy side and at the same time provides a convex equation, which is amenable to a minimization process and increased precision in the final result. The $\hat{\mathfrak{D}}^{2}$ yields an equation similar to the non-relativistic one, yet in a four-component framework, where Multiwavelet tools and algorithms developed for the non-relativistic case can be employed with minor modifications. On the other hand, the use of Multiwavelets is here essential to achieve the full potential of the approach. We implemented and validated this approach for one- and two-electron systems with increasing nuclear charge. Numerical tests were performed to gauge the actual precision of the approach with respect to either analytical reference values when possible or numerical results obtained with the \textit{GRASP} code otherwise.

physics.chem-ph↗

arXiv2026

Insights of Ammonia Decomposition on W--B Nanoclusters by Computational Simulations

Tungsten-boride nanoclusters represent a promising class of materials for catalytic applications, yet their structural stability and reactivity remain poorly understood. The evolutionary algorithm combined with density functional theory (DFT) are used to systematically explore the ground-state structures and stability landscape of W$_m$B$_n$ nanoclusters with up to 43 atoms. The resulting stability maps reveal a highly non-monotonic landscape characterized by isolated "magic" compositions, including WB$_{16}$, W$_2$B$_8$, W$_7$B$_{24}$, and W$_{11}$B$_{22}$, which exhibit pronounced local stability maxima. We further investigate the adsorption and initial decomposition step of ammonia on these clusters as a probe of their catalytic potential. Molecular NH$_3$ adsorption occurs exclusively on tungsten sites with energies ranging from -0.54 to -1.78 eV (average -1.43 eV), comparable to Pt$_n$ and Fe$_n$ clusters. Atomic hydrogen adsorption spans a broader range from +0.49 to -1.46 eV, reflecting high site sensitivity. Nudged elastic band calculations for the first N--H bond cleavage reveal forward barriers of 1.1-1.4 eV, with the dissociated NH$_2^*$ + H$^*$ state lying below the molecular adsorption state for most compositions. Notably, the activation barrier depends critically on the local environment available for stabilizing the detached hydrogen atom. These findings establish W--B nanoclusters as tunable catalysts for ammonia decomposition and provide a structural foundation for their rational design.

cond-mat.mtrl-sci↗

arXiv2026

Nonisothermal global-pressure exactness in fractured multiphase flow with aperture feedback

Global-pressure formulations recast multiphase Darcy flow in terms of a single pressure driving the total flux. Their exact equivalence to phase-pressure formulations holds only when the constitutive data satisfy the compatibility conditions required for a total-differential structure and its generalized nonisothermal extension. Here, we derive the exactness criterion for temperature-dependent mobilities and capillary pressures. We show that equivalence depends on whether the mobility-weighted capillary contribution is path independent in the saturation--temperature domain, so that it can be absorbed into a scalar global pressure. This yields the classical compatibility conditions within the saturation sector and a distinct mixed saturation--temperature condition that arises only in nonisothermal settings. We then incorporate this structure into a reduced matrix--fracture model with heat transport, matrix--fracture thermal exchange, and evolving aperture. Numerical benchmarks recover the three regimes predicted by the theory: globally exact, exact on each fixed-temperature slice but not on the full saturation--temperature domain, and fully nonexact. In fractured systems, thermal forcing alone can drive transitions between these regimes, while aperture evolution changes the path through state space. When saturation-sector exactness is lost, a least-squares projection on fixed-temperature slices extracts the nearest gradient component of the mobility-weighted capillary field. This yields a conservative slice-wise scalar-pressure surrogate and a quantitative projection residual. The residual separates saturation-sector nonintegrability from the mixed saturation--temperature incompatibility that controls genuinely nonisothermal loss of exactness. The framework links nonisothermal exactness theory, fractured-flow dynamics, and conservative reduced closure in a global-pressure formulation.

physics.flu-dyn↗

arXiv2026

Global Buckley-Leverett theory for multicomponent flow in fractured media: Isothermal equation-of-state coupling and dynamic capillarity

We present an isothermal Global Buckley--Leverett framework for multicomponent, multiphase flow in porous and fractured media that retains the interpretability of classical Buckley--Leverett while incorporating essential physics: equation of state-based phase behavior, multicomponent Maxwell--Stefan diffusion, dynamic capillarity, stress-sensitive permeability, and non-Darcy fracture flow. The formulation yields a single global-pressure equation driving the total Darcy flux and an exact fractional-flow decomposition of phase velocities with buoyancy and capillary drifts; inertial effects enter as per-phase damping that renormalizes mobilities. Crucially, the combination of Maxwell--Stefan diffusion and dynamic capillarity renders transport pseudo-parabolic, resolving the loss of strict hyperbolicity that plagues three-phase Buckley--Leverett and ensuring a well-posed initial-value problem. In practice, each time step solves the scalar global-pressure equation, reconstructs phase fluxes via the split, and advances strictly conservative component balances; axisymmetric (cylindrical) forms for radial injection with vertical buoyancy are provided. The model reduces exactly to classical Buckley--Leverett when added physics are disabled, making it a practical backbone for carbon storage, geothermal exchange, and contaminant transport in fractured, compositionally complex reservoirs.

physics.flu-dyn↗

arXiv2026

Quaternionic superconductivity links spinful pairing, topology, and charge-$4e$ order

We recast spinful superconductivity as a \textit{quaternion field theory}, where a quaternion is a four-component hypercomplex number with units $(\boldsymbol{e}_x,\boldsymbol{e}_y,\boldsymbol{e}_z)$, that encodes the spin-singlet/triplet gap in a single field $q(\mathbf{k})$. This yields a compact Bogoliubov-de Gennes (BdG) Hamiltonian $H_{\rm BdG}=ξ_{\mathbf{k}}τ_z+τ_+q+τ_-\,q^\ddagger$ and keeps time-reversal symmetry, Altland-Zirnbauer classification, and topological diagnostics in the same variables. In general the mixed singlet--triplet spectrum is branch-split, while the familiar perfect-square form is recovered only for unitary pairing. We introduce a quarteting field $Q\!\propto\!\mathrm{Sc}(q^2)$ and a minimal Ginzburg-Landau (GL) functional with covariant derivatives $(\nabla-2ie\mathbf A)q$ and $(\nabla-4ie\mathbf A)Q$. Analytically, a one-loop evaluation of the fluctuation bubble $Π(0)$ gives a quantitative vestigial charge-$4e$ criterion $μ_{\rm eff}=μ-\frac{g^2}{2}Π(0)<0$. Numerically, we verified: (i) a two-dimensional (2D) class-DIII lattice model whose $\mathbb{Z}_2$ index, computed from the occupied BdG eigenvectors via the standard sewing-matrix (Pfaffian) construction at time-reversal-invariant momenta, matches helical edge spectra; (ii) a GL simulation of a pure-$Q$ vortex carrying $h/4e$ flux within $\sim2\%$ and exhibiting $ξ_Q\!\propto\!\sqrt{η/|μ_{\rm eff}|}$; and (iii) a short-junction current-phase relation with a controlled window where the second harmonic dominates ($I_2\!\gg\!I_1$), together with doubled alternating-current Josephson emission and a Shapiro response consistent with $4e$-dominated transport. The framework provides a compact, symmetry-faithful route from microscopic pairing to device-level charge-$4e$ signatures.

cond-mat.supr-con↗

arXiv2026

A Fixed-Grid Affine-Constrained Multiwavelet Coefficient Method for Buckley--Leverett Shock Capturing

We present a fixed-grid conservative affine-constrained modal/multiwavelet coefficient method for one-dimensional Buckley--Leverett saturation transport. The saturation is evolved directly in a local orthonormal coefficient basis with a mean/detail structure: the first mode carries the conservative cell average, whereas higher modes carry zero-mean local details. The hyperbolic inflow condition is imposed as a linear trace constraint on the coefficient vector and enforced by affine lifting. For $(p>1)$, the boundary reprojection is applied in the detail subspace of the inflow cell, so that the prescribed trace is restored without modifying the conservative cell-average update. The transport operator is discretized in conservative weak form with monotone numerical fluxes, and shock-induced oscillations are controlled by a troubled-cell limiter acting on modal details. The method is validated on a Berea-core waterflood benchmark against an independent \texttt{pywaterflood} reference solution using the same Corey fractional-flow closure, physical parameters, and pore-volume-injected scaling. The affine-constrained coefficient solver reproduces the reference breakthrough curve and saturation profiles, preserves the imposed inflow trace to roundoff accuracy, controls saturation bounds through mean-preserving detail rescaling, and gives small accumulated global mass-balance defects. Mesh-refinement, flux-comparison, and modal-order studies show that $(p=2)$, corresponding to a piecewise-linear local representation, provides the most favorable accuracy--cost compromise among the tested orders for this shock-dominated benchmark.

physics.flu-dyn↗

arXiv2026

Representative-volume sizing in finite cylindrical computed tomography by low-wavenumber spectral convergence

Choosing a representative element volume (REV) from finite cylindrical Computed Tomography (CT) scans becomes ambiguous when a key field variable exhibits a slow axial trend, reflecting either geological variability or CT acquisition/reconstruction artifacts. In such cases, estimated statistics may vary systematically with subvolume size and position rather than converging by simple averaging. We present a practical workflow for sizing an REV under nonstationary conditions by first suppressing axial drift/trend to obtain a residual field suitable for second-order analysis, and then selecting the smallest analysis diameter for which the low-wavenumber spectral content stabilizes within a prescribed tolerance. The method is demonstrated on \textit{Thalassinoides}-bearing rocks, where branching burrow networks introduce heterogeneity at length scales comparable to laboratory core diameters, making imaging-based microstructural statistics and digital-rock estimates sensitive to subvolume choice. From segmented data, we define a scalar ``burrowsity'' field capturing burrow-related pore spaces and infills. Axial detrending, with optional normalization, mitigates acquisition drift and nonstationary trends, while covariance/spectral convergence is evaluated on nested cylinders consistent with the core geometry. Representativeness is posed as diameter convergence on nested inscribed cylinders: the two-point covariance and isotropic spectrum $\widehat{C}$ are estimated, and the smallest diameter at which the low-wavenumber plateau becomes stable is selected. Applied to a segmented \textit{Thalassinoides} core, the method gives $D_{\mathrm{REV}}\simeq 93~\mathrm{mm}$ and $H_{\mathrm{REV}}\simeq 83~\mathrm{mm}$, enabling reproducible correlation-scale reporting and connectivity-sensitive property estimation.

cond-mat.soft↗

arXiv2026

Capillarity in Stationary Random Granular Media: Distribution-Aware Screening and Quantitative Supercell Sizing

We develop a quantitative framework to determine the minimal periodic supercell required for representative simulations of capillarity-screened Darcy flow in stationary random, polydisperse granular media. The microstructure is characterized by two-point statistics (covariance and spectral density) that govern finite-size fluctuations. Capillarity is modeled as a screened, modified-Helmholtz problem with phase-dependent transport under periodic boundary conditions; periodic homogenization yields an apparent conductivity, an apparent screening parameter, and a macroscopic capillary decay length. Because screening imparts a spatial low-pass response, we introduce a distribution-aware treatment of polydispersity consisting of a capillarity-weighted volume fraction and a screened analogue of the integral range that preserves variance units and recovers classical descriptors in the appropriate limits. These descriptors lead to two sizing rules: (i) a length criterion on the shortest cell edge controlled by a microstructural correlation length, the macroscopic decay length, and a high quantile of grain size; and (ii) a volume criterion that links the target coefficient of variation to the screened integral range and the phase contrast. The framework couples statistical microstructure information to capillary response and yields reproducible, distribution-aware supercell selection for image-based finite-element or fast-Fourier-transform solvers. The resulting criteria are therefore intended for representativity of the coarse-grained screened response, rather than for isolated nonlinear pore-scale events.

cond-mat.soft↗

arXiv2025

Gauge-Invariant Long-Wavelength TDDFT Without Empty States: From Polarizability to Kubo Conductivity Across Heterogeneous Materials

Electromagnetic response is commonly computed in two languages: length-gauge molecular polarizabilities and velocity-gauge (Kubo) conductivities for periodic solids. We introduce a compact, gauge-invariant bridge that carries the same microscopic inputs-transition dipoles and interaction kernels-from molecules to crystals and heterogeneous media, with explicit SI prefactors and fine-structure scaling via $(α_{\rm fs})$. The long-wavelength limit is handled through a reduced dielectric matrix that retains local-field mixing, interfaces and 2D layers are treated with sheet boundary conditions (rather than naïve ultrathin films), and length-velocity equivalence is enforced in practice by including the equal-time (diamagnetic/contact) term alongside the paramagnetic current. Finite temperature is addressed on the Matsubara axis with numerically stable real-axis evaluation (complex polarization propagator), preserving unit consistency end-to-end. The framework enables predictive, unit-faithful observables from radio frequency to ultraviolet-RF/microwave heating and penetration depth, dielectric-logging contrast, interfacial optics of thin films and 2D sheets, and adsorption metrics via imaginary-axis polarizabilities. Numerical checks (gauge overlay and optical $(f)$-sum saturation) validate the implementation. Immediate priorities include compact, temperature- and salinity-aware kernels with quantified uncertainties and \emph{operando} interfacial diagnostics for integration into multiphysics digital twins.

cond-mat.mtrl-sci↗

arXiv2025

Low-temperature behavior of density-functional theory for metals based on density-functional perturbation theory and Sommerfeld expansion

The temperature dependence of most solid-state properties is dominated by lattice vibrations, but metals display notable purely electronic effects at low temperature, such as the linear specific heat and the linear entropy, that were derived by Sommerfeld for the non-interacting electron gas via the low-temperature expansion of Fermi-Dirac integrals. Here we treat temperature as a perturbation within density-functional perturbation theory (DFPT). For finite temperature, we show how self-consistency screens the bare, temperature-induced density change obtained in the non-interacting picture: the inverse transpose of the electronic dielectric operator, that includes Adler-Wiser and a term related to the shift in Fermi level, links the self-consistent density response to the bare thermal density change. This approach is implemented in DFTK, and demonstrated by the computation of the second-order derivative of the free energy, and the first-order derivative of entropy for aluminum. Then, we examine the $T\!\to\!0$ limit. The finite temperature formalism contains divergences, that we cure using the Sommerfeld expansion to analyze metallic systems at 0 K. The electronic free energy is quadratic in $T$ provided the Fermi level is not at a Van Hove singularity of the density of states. If the latter happens, another temperature behavior might appear, depending on the type of Van Hove singularity, that we analyze. Our formulation applies to systems periodic in one, two, or three dimensions, and provides a basis for studying temperature-dependent electronic instabilities (e.g., charge-density waves) within density-functional theory and DFPT.

cond-mat.mtrl-sci↗

arXiv2025

A basis-free, octonionic criterion for Weyl points in solids

Standard ways of locating and characterizing Weyl points--Berry-flux integrals on small spheres and local $k\cdot p$ fits--are topologically sound but depend on user choices (sphere center/radius, gauge smoothing, surface charting, and Pauli-frame transport) that complicate high-throughput workflows. We introduce a local, basis-free criterion that avoids these knobs by using the octonionic geometry of $\operatorname{Im}\mathbb{O}\cong\mathbb{R}^7$. From a smooth two-band projector we build a unit octonion field $u(\mathbf{k})$ and its octonionic connection $\mathcal{A}_i=\operatorname{Im}(\bar u\,\partial_{k_i}u)$. Contracting the three directional derivatives with the $\mathrm{G}_2$-invariant three-form produces a pseudoscalar density whose sign gives the node's chirality. A companion quantity--the octonionic associator--vanishes at leading order precisely when the local three directions close inside an associative (quaternionic) three-plane; its smallness thus provides an intrinsic, pointwise self-consistency check that the two-band reduction is valid. The construction is invariant under $\mathrm{SU}(2)$ gauge changes of the two-band subspace and under $\mathrm{G}_2$ rotations of its completion, and it eliminates enclosing surfaces and gauge seams. In the linear regime the density reduces to the oriented volume set by the velocity matrix, thereby agreeing with the Chern number on a small sphere and with the chirality obtained from a $k\cdot p$ linearization. We outline a practical stencil-based algorithm compatible with Wannier tight-binding Hamiltonians and demonstrate robustness to benign numerical choices, while providing an intrinsic warning signal near band entanglement or multi-fold touchings.

cond-mat.mtrl-sci↗

arXiv2025

Abinit 2025: New Capabilities for the Predictive Modeling of Solids and Nanomaterials

Abinit is a widely used scientific software package implementing density functional theory and many related functionalities for excited states and response properties. This paper presents the novel features and capabilities, both technical and scientific, which have been implemented over the past 5 years. This evolution occurred in the context of evolving hardware platforms, high-throughput calculation campaigns, and the growing use of machine learning to predict properties based on databases of first principles results. We present new methodologies for ground states with constrained charge, spin or temperature; for density functional perturbation theory extensions to flexoelectricity and polarons; and for excited states in many-body frameworks including GW, dynamical mean field theory, and coupled cluster. Technical advances have extended abinit high-performance execution to graphical processing units and intensive parallelism. Second principles methods build effective models on top of first principles results to scale up in length and time scales. Finally, workflows have been developed in different community frameworks to automate \abinit calculations and enable users to simulate hundreds or thousands of materials in controlled and reproducible conditions.

cond-mat.mtrl-sci↗

arXiv2025

Actively-trained magnetic Moment Tensor Potentials for mechanical, dynamical, and thermal properties of paramagnetic CrN

We present a protocol for automated fitting of magnetic Moment Tensor Potential explicitly including magnetic moments in its functional form. For the fitting of this potential we use energies, forces, stresses, and magnetic forces (negative derivatives of energies with respect to magnetic moments) of configurations selected with an active learning algorithm. These selected configurations are computed using constrained density functional theory, which enables calculating energies and their derivatives for both equilibrium and non-equilibrium (excited) magnetic states. We test our protocol on the system of B1-CrN and demonstrate that the automatically trained magnetic Moment Tensor Potential reproduces mechanical, dynamical, and thermal properties, of B1-CrN in the paramagnetic state with respect to density functional theory and experiments.

cond-mat.mtrl-sci↗

arXiv2024

Quantum Modelling of Magnetism in Strongly Correlated Materials: Evaluating Constrained DFT and the Hubbard Model for Y114

Transition-metal compounds represent a fascinating playground for exploring the intricate relationship between structural distortions, electronic properties, and magnetic behaviour, holding significant promise for technological advancements. Among these compounds, YBaCo$_4$O$_{7}$ (Y114) is attractive due to its manifestation of a ferrimagnetic component at low temperature intertwined with distortion effect due to the charge disproportionation on Co ions, exerting profound impact on its magnetic properties. In this perspective paper, we study the structural and magnetic intricacies of the Y114 crystal using a novel first-principles methodology. Traditionally, the investigation of such materials has relied heavily on computational modelling using density-functional theory (DFT) with the on-site Coulomb interaction correction $U$ (DFT+$U$) based on the Hubbard model (sometimes including Hund's exchange coupling parameter $J$, DFT+$U$+$J$) to unravel their complexities. Herein, we analysed the spurious effects of magnetic-moment delocalisation and spillover to non-magnetic ions in the lattice on electronic structure and magnetic properties of Y114. To overcome this problem we have applied constrained DFT (cDFT) based on the potential self-consistency approach, and comprehensively explore the Y114 crystal's characteristics in its ferrimagnetic order. We find that cDFT yields magnetic moments of Co ions much closer to the experimental values than Hubbard model with the parameters $U$ and $J$ fitted to reproduce experimental lattice constants. cDFT allows for an accurate prediction of magnetic properties using oxidation states of magnetic ions as well-defined parameters. Through this perspective, we not only enhance our understanding of the magnetic interactions in Y114 crystal, but also pave the way for future investigations into magnetic materials.

cond-mat.str-el↗