arXiv subjects

Szymon Smiga

Publications and source records attributed to Szymon Smiga.

7 recordsLinked to original sources

arXiv2026

A Unified Dielectric-Dependent Hybrid Functional for Accurate Band Gaps across Dimensions

Predicting fundamental band gaps across material classes and dimensionalities remains a central challenge in electronic-structure theory. Here, we show that intrinsic dielectric screening provides a unified control parameter for nonlocal exchange from bulk to low-dimensional and heterogeneous materials. We introduce a geometry-independent dielectric response and incorporate it self-consistently into a nonempirical screened-dielectric-dependent hybrid functional. Benchmarks for 100 materials spanning bulk, two-dimensional, one-dimensional, and mixed-dimensional systems show near-GW accuracy at the computational cost of generalized Kohn-Sham theory. These results reveal a screening-exchange-gap relation in which reduced dimensionality weakens intrinsic dielectric screening, strengthens nonlocal exchange, and drives the opening of fundamental gaps.

cond-mat.mtrl-sci↗

arXiv2026

Nonlocal Orbital-Free Kinetic Energy Functional from the Jellium-with-Gap Model for Finite Systems

The quasi-linear scaling of orbital-free density functional theory (OF-DFT) with system size makes it a computationally efficient alternative to conventional Kohn--Sham density functional theory for many condensed-matter applications. However, its applicability remains limited, particularly for finite systems such as molecular clusters, due to the lack of accurate kinetic energy density functionals. In this context, the development of nonlocal kinetic energy density functionals (NL-KEDFs) has significantly advanced the practical utility of OF-DFT. Here, following an alternative formulation based on the linear-response kernel derived from the jellium-with-gap model (JGM), we develop an NL-KEDF capable of accurately describing the diverse density regimes characteristic of finite systems, including molecular clusters. Benchmark calculations, together with an analysis of the corresponding Pauli potentials, demonstrate that the proposed functional achieves higher accuracy than state-of-the-art orbital-free approaches for finite systems. Furthermore, the optical properties computed using the present method show good agreement with reference results, highlighting its reliability. These results indicate that the proposed NL-KEDF provides a robust and efficient framework for extending OF-DFT to finite systems, with potential implications for nanomaterial design and a deeper understanding of nanoscale phenomena.

cond-mat.mtrl-sci↗

arXiv2025

Meta-GGA dielectric-dependent and range-separated screened hybrid functional for reliable prediction of material properties

We propose a range-separated hybrid exchange-correlation functional to calculate solid-state material properties. The functional mixes Hartree-Fock exchange with the semilocal exchange of the meta-generalized gradient approximation (meta-GGA) and the fraction of Hartree-Fock exchange is determined from the dielectric function. First-principles calculations and comparison with other meta-GGA approximations show that the functional leads to reasonably good performance for the band gap and optical properties. We also show that the present functional also successfully resolves the well-known ``band gap problem'' of narrow gap Cu-based semiconductors, such as Cu3SbSe4 and Cu3AsSe4, where, in general, a considerably large band inversion energy leads to a ``false'' negative or metallic band gap for all other methods. Furthermore, reasonable accuracy for the occupied d-bands and transition energies is also obtained for bulk solids. Thus, overall, our results demonstrate the predictive power of range-separated meta-GGA hybrid functionals for quantum materials simulations.

cond-mat.mtrl-sci↗

arXiv2023

Semilocal Meta-GGA Exchange-Correlation Approximation From Adiabatic Connection Formalism: Extent and Limitations

The incorporation of a strong interaction regime within the approximate, semilocal exchange-correlation functionals still remains a very challenging task for density functional theory. One of the promising attempts in this direction is the recently proposed adiabatic connection semilocal correlation (ACSC) approach [Phys. Rev. B 2019, 99, 085117] allowing to construct the correlation energy functionals by interpolation of the high and low-density limits for the given semi-local approximation. The current study extends the ACSC method to the meta-GGA level of theory, providing some new insights. As an example, we construct the correlation energy functional base on the high and low-density limits of the Tao-Perdew-Starverov-Scuseria (TPSS) functional. Arose in this way TPSS-ACSC functional is one electron self-interaction free, accurate for the strictly correlated, and quasi-two-dimensional regimes. Based on simple examples, we show the advantages and disadvantages of ACSC semi-local functionals and provide some new guidelines for future developments in this context.

cond-mat.other↗

arXiv2021

Improving the applicability of the Pauli kinetic energy density based semilocal functional for solids

The Pauli kinetic energy enhancement factor $α=(τ-τ^W)/τ^{unif}$ is an important density ingredient, used to construct many meta-generalized gradient approximations (meta-GGA) exchange-correlation (XC) energy functionals, including the very successful strongly constrained and appropriately normed (SCAN) semilocal functional. Another meta-GGA functional, known as MGGAC [Phys. Rev. B 100, 155140 (2019)], is also proposed in recent time depending only on the $α$ ingredient and based on the generalization of the Becke-Roussel approach with the cuspless hydrogen exchange hole density. The MGGAC functional is proved to be a very useful and competitive meta-GGA semilocal functional for electronic structure properties of solids and molecules. Based on the successful implication of the ingredient $α$, which is also useful to construct the one-electron self-interaction free correlation energy functional, here we propose revised correlation energy for MGGAC exchange functional which is more accurate and robust, especially for the high and low-density limits of the uniform density scaling. The present XC functional, named as revised MGGAC (rMGGAC), shows an impressive improvement for the structural and energetic properties of solids compared to its previous version. Moreover, the assessment of the present constructed functional shows to be quite useful in solid-state physics in terms of addressing several current challenging solid-state problems.

cond-mat.mtrl-sci↗

arXiv2019

Self-consistent range-separated density-functional theory with second-order perturbative correction via the optimized-effective-potential method

We extend the range-separated double-hybrid RSH+MP2 method [J. G. Angyan et al., Phys. Rev. A 72, 012510 (2005)], combining long-range HF exchange and MP2 correlation with a short-range density functional, to a fully self-consistent version using the optimized-effective-potential technique in which the orbitals are obtained from a local potential including the long-range HF and MP2 contributions. We test this approach, that we name RS-OEP2, on a set of small closed-shell atoms and molecules. For the commonly used value of the range-separation parameter $μ=0.5$ bohr$^{-1}$, we find that self-consistency does not seem to bring any improvement for total energies, ionization potentials, and electronic affinities. However, contrary to the non-self-consistent RSH+MP2 method, the present RS-OEP2 method gives a LUMO energy which physically corresponds to a neutral excitation energy and gives local exchange-correlation potentials which are reasonably good approximations to the corresponding Kohn-Sham quantities. At a finer scale, we find that RS-OEP2 gives largely inaccurate correlation potentials and correlated densities, which points to the need of further improvement of this type of range-separated double hybrids.

physics.chem-ph↗

arXiv2016

Self-consistent double-hybrid density-functional theory using the optimized-effective-potential method

We introduce an orbital-optimized double-hybrid (DH) scheme using the optimized-effective-potential (OEP) method. The orbitals are optimized using a local potential corresponding to the complete exchange-correlation energy expression including the second-order M{ø}ller-Plesset (MP2) correlation contribution. We have implemented a one-parameter version of this OEP-based self-consistent DH scheme using the BLYP density-functional approximation and compared it to the corresponding non-self-consistent DH scheme for calculations on a few closed-shell atoms and molecules. While the OEP-based self-consistency does not provide any improvement for the calculations of ground-state total energies and ionization potentials, it does improve the accuracy of electron affinities and restores the meaning of the LUMO orbital energy as being connected to a neutral excitation energy. Moreover, the OEP-based self-consistent DH scheme provides reasonably accurate exchange-correlation potentials and correlated densities.

physics.chem-ph↗