Dr Nikitas Gidopoulos' Outputs (27)

Electrostatics of metallic surfaces in periodic density functional theory simulations within and beyond the linear response regime (2023)
Journal Article
Scivetti, I., Gidopoulos, N. I., & Teobaldi, G. (2023). Electrostatics of metallic surfaces in periodic density functional theory simulations within and beyond the linear response regime. Physical Review B, 108(16), Article 165423. https://doi.org/10.1103/PhysRevB.108.165423

It has been more than fifty years already since the first ever Density Functional Theory (DFT) simulation of a jellium surface demonstrated that uniform electric fields and external point charges induce equivalent electrostatics in the limit of linea... Read More about Electrostatics of metallic surfaces in periodic density functional theory simulations within and beyond the linear response regime.

Effective local potentials for density and density-matrix functional approximations with non-negative screening density (2023)
Journal Article
Pitts, T. C., Bousiadi, S., Gidopoulos, N. I., & Lathiotakis, N. N. (2023). Effective local potentials for density and density-matrix functional approximations with non-negative screening density. The Journal of Chemical Physics, 158(18), Article 184105. https://doi.org/10.1063/5.0143757

A way to improve the accuracy of the spectral properties in density functional theory (DFT) is to impose constraints on the effective, Kohn-Sham (KS), local potential [J. Chem. Phys. 136, 224109 (2012)]. As illustrated, a convenient variational quant... Read More about Effective local potentials for density and density-matrix functional approximations with non-negative screening density.

DFT Exchange: Sharing Perspectives on the Workhorse of Quantum Chemistry and Materials Science (2022)
Journal Article
Teale, A. M., Helgaker, T., Savin, A., Adano, C., Aradi, B., Arbuznikov, A. V., Ayers, P., Baerends, E. J., Barone, V., Calaminici, P., Cances, E., Carter, E. A., Chattaraj, P. K., Chermette, H., Ciofini, I., Crawford, T. D., De Proft, F., Dobson, J., Draxl, C., Frauenheim, T., …Yang, W. (2022). DFT Exchange: Sharing Perspectives on the Workhorse of Quantum Chemistry and Materials Science. Physical Chemistry Chemical Physics, 24(47), 28700-28781. https://doi.org/10.1039/d2cp02827a

In this paper, the history, present status, and future of density-functional theory (DFT) is informally reviewed and discussed by 70 workers in the field, including molecular scientists, materials scientists, method developers and practitioners. The... Read More about DFT Exchange: Sharing Perspectives on the Workhorse of Quantum Chemistry and Materials Science.

Density inversion method for local basis sets without potential auxiliary functions: inverting densities from RDMFT (2022)
Journal Article
Bousiadi, S., Gidopoulos, N. I., & Lathiotakis, N. N. (2022). Density inversion method for local basis sets without potential auxiliary functions: inverting densities from RDMFT. Physical Chemistry Chemical Physics, 24(32), 19279-19286. https://doi.org/10.1039/d2cp01866g

A density inversion method is presented, to obtain the constrained, optimal, local potential that has a prescribed asymptotic behaviour and reproduces optimally any given ground-state electronic density. This work builds upon the method of [Callow et... Read More about Density inversion method for local basis sets without potential auxiliary functions: inverting densities from RDMFT.

Density functionals with spin-density accuracy for open shells (2022)
Journal Article
Callow, T., Pearce, B., & Gidopoulos, N. (2022). Density functionals with spin-density accuracy for open shells. The Journal of Chemical Physics, 156(11), Article 111101. https://doi.org/10.1063/5.0071991

Electrons in zero external magnetic field can be studied with density functional theory (DFT) or with spin-DFT (SDFT). The latter is normally used for open shell systems because its approximations appear to model better the exchange and correlation (... Read More about Density functionals with spin-density accuracy for open shells.

Enhanced electron-phonon coupling near an electronic quantum phase transition (2022)
Journal Article
Gidopoulos, N. (2022). Enhanced electron-phonon coupling near an electronic quantum phase transition. Journal of Physics: Condensed Matter, 34(14), Article 14LT01. https://doi.org/10.1088/1361-648x/ac4dbe

I construct a simple model to demonstrate that when the manyelectron quantum state of a material is near a quantum phase transition and the vibrational motion of a phonon explores the potential energy surface near the transition point, then an impene... Read More about Enhanced electron-phonon coupling near an electronic quantum phase transition.

Generalized Kohn–Sham equations with accurate total energy and single-particle eigenvalue spectrum (2021)
Journal Article
Pitts, T. C., Lathiotakis, N. N., & Gidopoulos, N. (2021). Generalized Kohn–Sham equations with accurate total energy and single-particle eigenvalue spectrum. The Journal of Chemical Physics, 155(22), Article 224105. https://doi.org/10.1063/5.0071205

We propose a new generalized Kohn–Sham or constrained hybrid method, where the exchange potential is the (equally weighted) average of the nonlocal Fock–exchange term and the self-interaction-corrected exchange potential, as obtained from our constra... Read More about Generalized Kohn–Sham equations with accurate total energy and single-particle eigenvalue spectrum.

Improving the exchange and correlation potential in density-functional approximations through constraints (2020)
Journal Article
Callow, T. J., Pearce, B. J., Pitts, T., Lathiotakis, N., Hodgson, M. J., & Gidopoulos, N. I. (2020). Improving the exchange and correlation potential in density-functional approximations through constraints. Faraday Discussions, 224, 126-144. https://doi.org/10.1039/d0fd00069h

We review and expand on our work to impose constraints on the effective Kohn–Sham (KS) potential of local and semi-local density-functional approximations. Constraining the minimisation of the approximate total energy density-functional invariably le... Read More about Improving the exchange and correlation potential in density-functional approximations through constraints.

Density-inversion method for the Kohn-Sham potential: role of the screening density (2020)
Journal Article
Callow, T., Lathiotakis, N., & Gidopoulos, N. (2020). Density-inversion method for the Kohn-Sham potential: role of the screening density. The Journal of Chemical Physics, 152(16), Article 164114. https://doi.org/10.1063/5.0005781

We present a method to invert a given density and find the Kohn–Sham (KS) potential in Density Functional Theory (DFT) that shares the density. Our method employs the concept of screening density, which is naturally constrained by the inversion proce... Read More about Density-inversion method for the Kohn-Sham potential: role of the screening density.

Optimal power series expansions of the Kohn-Sham potential (2018)
Journal Article
Callow, T. J., & Gidopoulos, N. I. (2018). Optimal power series expansions of the Kohn-Sham potential. The European Physical Journal B, 91(10), Article 209. https://doi.org/10.1140/epjb/e2018-90189-2

A fundamental weakness of density functional theory (DFT) is the difficulty in making systematic improvements to approximations for the exchange and correlation functionals. In this paper, we follow a wave-function-based approach [N.I. Gidopoulos, Ph... Read More about Optimal power series expansions of the Kohn-Sham potential.

Performance of the Constrained Minimization of the Total Energy in Density Functional Approximations: the Electron Repulsion Density and Potential (2018)
Journal Article
Pitts, T., Gidopoulos, N., & Lathiotakis, N. (2018). Performance of the Constrained Minimization of the Total Energy in Density Functional Approximations: the Electron Repulsion Density and Potential. The European Physical Journal B, 91(6), Article 130. https://doi.org/10.1140/epjb/e2018-90123-8

In the constrained minimization method of Gidopoulos and Lathiotakis [N.I. Gidopoulos, N.N. Lathiotakis, J. Chem. Phys. 136, 224109 (2012)], the Hartree exchange and correlation Kohn-Sham potential of a finite N-electron system is replaced by the ele... Read More about Performance of the Constrained Minimization of the Total Energy in Density Functional Approximations: the Electron Repulsion Density and Potential.

Self-interaction free local exchange potentials applied to metallic systems (2017)
Journal Article
Clark, S. J., Hollins, T. W., Refson, K., & Gidopoulos, N. I. (2017). Self-interaction free local exchange potentials applied to metallic systems. Journal of Physics: Condensed Matter, 29(37), Article 374002. https://doi.org/10.1088/1361-648x/aa7ba6

We extend the formalism of local exchange methods to calculate and investigate the electronic structure of metals. It is well-known that the Hartree-Fock method when applied to metals shows unphysical behaviour, however the accurate treatment of exch... Read More about Self-interaction free local exchange potentials applied to metallic systems.

A local Fock-exchange potential in Kohn–Sham equations (2016)
Journal Article
Hollins, T., Clark, S., Refson, K., & Gidopoulos, N. (2017). A local Fock-exchange potential in Kohn–Sham equations. Journal of Physics: Condensed Matter, 29(4), Article 04LT01. https://doi.org/10.1088/1361-648x/29/4/04lt01

We derive and employ a local potential to represent the Fock exchange operator in electronic single-particle equations. This local Fock-exchange (LFX) potential is very similar to the exact exchange (EXX) potential in density functional theory (DFT).... Read More about A local Fock-exchange potential in Kohn–Sham equations.

Chapter Eleven - Excitation Energies of Molecules from Ensemble Density Functional Theory: Multiconfiguration Approaches (2015)
Book Chapter
Pernal, K., Gidopoulos, N. I., & Pastorczak, E. (2015). Chapter Eleven - Excitation Energies of Molecules from Ensemble Density Functional Theory: Multiconfiguration Approaches. In P. E. Hoggan, & T. Ozdogan (Eds.), Electron correlation in molecules – ab initio beyond Gaussian quantum chemistry (199-229). Elsevier. https://doi.org/10.1016/bs.aiq.2015.06.001

Orbitals from local RDMFT: Are they Kohn-Sham or Natural Orbitals? (2015)
Journal Article
Theophilou, I., Lathiotakis, N., Gidopoulos, N., Rubio, A., & Helbig, N. (2015). Orbitals from local RDMFT: Are they Kohn-Sham or Natural Orbitals?. The Journal of Chemical Physics, 143(5), https://doi.org/10.1063/1.4927784

Recently, an approximate theoretical framework was introduced, called local reduced density matrix functional theory (local-RDMFT), where functionals of the one-body reduced density matrix (1-RDM) are minimized under the additional condition that the... Read More about Orbitals from local RDMFT: Are they Kohn-Sham or Natural Orbitals?.

Chapter Six – Constrained Local Potentials for Self-Interaction Correction (2015)
Book Chapter
Gidopoulos, N., & Lathiotakis, N. (2015). Chapter Six – Constrained Local Potentials for Self-Interaction Correction. In E. Arimondo, P. R. Berman, & C. Lin (Eds.), Advances in atomic, molecular, and optical physics (129-142). Academic Press. https://doi.org/10.1016/bs.aamop.2015.06.003

In this chapter, we discuss a method to alleviate self-interaction (SI) errors from the approximate Kohn–Sham potential, but without altering the corresponding approximate exchange and correlation energy, which still remains contaminated with SIs. In... Read More about Chapter Six – Constrained Local Potentials for Self-Interaction Correction.

A correction for the Hartree-Fock density of states for jellium without screening (2015)
Journal Article
Blair, A., Kroukis, A., & Gidopoulos, N. (2015). A correction for the Hartree-Fock density of states for jellium without screening. The Journal of Chemical Physics, 142(8), Article 084116. https://doi.org/10.1063/1.4909519

We revisit the Hartree-Fock (HF) calculation for the uniform electron gas, or jellium model, whose predictions—divergent derivative of the energy dispersion relation and vanishing density of states (DOS) at the Fermi level—are in qualitative disagree... Read More about A correction for the Hartree-Fock density of states for jellium without screening.

Local reduced-density-matrix-functional theory: Incorporating static correlation effects in Kohn-Sham equations (2014)
Journal Article
Lathiotakis, N., Helbig, N., Rubio, A., & Gidopoulos, N. (2014). Local reduced-density-matrix-functional theory: Incorporating static correlation effects in Kohn-Sham equations. Physical Review A, 90(3), Article 032511. https://doi.org/10.1103/physreva.90.032511

We propose a scheme to bring reduced-density-matrix-functional theory into the realm of density functional theory (DFT) that preserves the accurate density functional description at equilibrium, while incorporating accurately static and left-right co... Read More about Local reduced-density-matrix-functional theory: Incorporating static correlation effects in Kohn-Sham equations.

Distinct Magnetic Phase Transition at the Surface of an Antiferromagnet (2014)
Journal Article
Langridge, S., Watson, G., Gibbs, D., Betouras, J., Gidopoulos, N., Pollmann, F., …Lander, G. (2014). Distinct Magnetic Phase Transition at the Surface of an Antiferromagnet. Physical Review Letters, 112(16), Article 167201. https://doi.org/10.1103/physrevlett.112.167201

In the majority of magnetic systems the surface is required to order at the same temperature as the bulk. In the present Letter, we report a distinct and unexpected surface magnetic phase transition at a lower temperature than the Néel temperature. E... Read More about Distinct Magnetic Phase Transition at the Surface of an Antiferromagnet.

Electronic non-adiabatic states: towards a density functional theory beyond the Born–Oppenheimer approximation (2014)
Journal Article
Gidopoulos, N., & Gross, E. (2014). Electronic non-adiabatic states: towards a density functional theory beyond the Born–Oppenheimer approximation. Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 372(2011), Article 20130059. https://doi.org/10.1098/rsta.2013.0059

A novel treatment of non-adiabatic couplings is proposed. The derivation is based on a theorem by Hunter stating that the wave function of the complete system of electrons and nuclei can be written, without approximation, as a Born–Oppenheimer (BO)-t... Read More about Electronic non-adiabatic states: towards a density functional theory beyond the Born–Oppenheimer approximation.