Dynamic charges effect on infrared dielectric response of polar materials
Pith reviewed 2026-06-29 06:57 UTC · model grok-4.3
The pith
Dynamic charge redistribution must be explicitly included to predict infrared dielectric responses accurately in polar materials at elevated temperatures.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
In rutile TiO2 with large Born effective charges, dynamic charge effects become increasingly important at elevated temperatures and are essential for accurately predicting longitudinal optical phonon features and infrared reflectance when computed via Green-Kubo molecular dynamics with a machine-learning neuroevolution potential that incorporates dynamic charges.
What carries the argument
Machine-learning neuroevolution potential with dynamic charges (qNEP) inside Green-Kubo molecular dynamics, which tracks real-time charge redistribution during thermal atomic motion.
If this is right
- Explicit treatment of dynamic charge evolution is required for accurate infrared optical properties in polar materials under thermal excitation.
- Dynamic charge effects increase in importance with rising temperature.
- Longitudinal optical phonon features are particularly sensitive to dynamic charge inclusion.
- Infrared reflectance predictions improve when dynamic charges are accounted for rather than held fixed.
Where Pith is reading between the lines
- The same dynamic-charge treatment may be needed in other polar materials that exhibit large Born effective charges.
- Device modeling for high-temperature infrared applications would benefit from replacing fixed-charge assumptions with evolving charges.
- Testing the method on additional polar crystals could reveal how general the temperature-dependent importance of dynamic charges is.
Load-bearing premise
The machine-learning potential with dynamic charges accurately reproduces the real-time charge redistribution that occurs in rutile TiO2 as atoms move during thermal motion.
What would settle it
High-temperature experimental infrared reflectance spectra of rutile TiO2 that diverge from fixed-charge simulations but align with dynamic-charge simulations.
Figures
read the original abstract
Predictive modeling of the infrared dielectric function in polar materials is crucial for thermal management and infrared devices design. While the Green-Kubo molecular dynamics (MD) framework provides a nonperturbative route to compute dielectric responses from dipole fluctuations, yet it commonly relies on the fixed-charge approximation that neglects dynamic charge redistribution during atomic motion. Here, we employ a machine-learning neuroevolution potential with dynamic charges (qNEP) combined with Green-Kubo MD to investigate the dynamic charge effect on the infrared dielectric response of rutile TiO$_2$, a material with large Born effective charges (BEC). Our results show that dynamic charge effects become increasingly important at elevated temperatures and are essential for accurately predicting longitudinal optical phonon features and infrared reflectance. This work establishes that accurate prediction of infrared optical properties in polar materials under thermal excitation requires explicit treatment of dynamic charge evolution.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript develops a qNEP machine-learning potential that incorporates dynamic charges and combines it with Green-Kubo MD to compute the infrared dielectric function of rutile TiO2. It reports that dynamic-charge fluctuations grow in importance with temperature and are required to correctly capture the LO phonon features and the resulting infrared reflectance spectra.
Significance. If the qNEP dynamic-charge predictions are shown to be faithful to the underlying DFT reference on thermal configurations, the work would establish a practical, non-perturbative route to temperature-dependent IR spectra in polar materials that avoids the fixed-charge approximation. This would be directly relevant to thermal-management and IR-device modeling.
major comments (2)
- [Methods] Methods section: no quantitative benchmark is supplied that compares the dynamic (Bader or Wannier) charges extracted from qNEP trajectories against DFT reference calculations performed on the same finite-temperature MD snapshots. Because the Green-Kubo spectrum is built directly from the fluctuating dipole, any systematic deviation in the dynamic charges would propagate into the reported LO features and temperature trends.
- [Results] Results section: the manuscript presents no direct comparison of the dynamic-charge spectra against either a fixed-charge baseline or against experimental infrared reflectance data at the same temperatures, leaving the magnitude of the claimed improvement unquantified.
minor comments (1)
- [Abstract] The abstract states that dynamic charges are 'essential' but does not define the quantitative criterion used to reach that conclusion.
Simulated Author's Rebuttal
We thank the referee for the constructive and detailed comments. We address each major point below and will revise the manuscript to incorporate the suggested benchmarks and comparisons.
read point-by-point responses
-
Referee: [Methods] Methods section: no quantitative benchmark is supplied that compares the dynamic (Bader or Wannier) charges extracted from qNEP trajectories against DFT reference calculations performed on the same finite-temperature MD snapshots. Because the Green-Kubo spectrum is built directly from the fluctuating dipole, any systematic deviation in the dynamic charges would propagate into the reported LO features and temperature trends.
Authors: We agree that this benchmark is important for validating the dynamic-charge model. In the revised manuscript we will add quantitative comparisons of the dynamic charges (computed with the same partitioning scheme used in the qNEP) obtained from DFT single-point calculations on multiple snapshots sampled from the finite-temperature qNEP MD trajectories at several temperatures. These results will be presented in the Methods section or as a supplementary figure to demonstrate that systematic deviations are small and do not alter the reported temperature trends in the LO features. revision: yes
-
Referee: [Results] Results section: the manuscript presents no direct comparison of the dynamic-charge spectra against either a fixed-charge baseline or against experimental infrared reflectance data at the same temperatures, leaving the magnitude of the claimed improvement unquantified.
Authors: We acknowledge the absence of these direct comparisons in the current version. We will revise the Results section to include explicit side-by-side plots and quantitative metrics (e.g., LO-TO splitting, peak positions, and integrated reflectance differences) between the dynamic-charge Green-Kubo spectra and the corresponding fixed-charge spectra obtained with temperature-averaged charges. For experimental validation we will add comparisons to available infrared reflectance measurements on rutile TiO2 at the temperatures where data have been reported, and we will discuss the level of agreement to better quantify the improvement attributable to dynamic charges. revision: yes
Circularity Check
No significant circularity; method application yields independent simulation results
full rationale
The derivation applies an existing qNEP model with dynamic charges inside the Green-Kubo MD framework to compute temperature-dependent dielectric spectra for rutile TiO2. No equations or procedures are described that define the target LO features or reflectance in terms of the fitted charges themselves, nor does any uniqueness theorem or ansatz from self-citation reduce the reported temperature dependence to a tautology. The central claim rests on explicit trajectory sampling rather than on re-labeling of inputs.
Axiom & Free-Parameter Ledger
Reference graph
Works this paper leans on
-
[1]
author author C. R. \ Gubbin , author S. De Liberato ,\ and\ author T. G. \ Folland ,\ title title Surface phonon polaritons for infrared optoelectronics , \ https://doi.org/10.1063/5.0064234 journal journal J. Appl. Phys. \ volume 131 ,\ pages 030901 ( year 2022 ) NoStop
-
[2]
author author J. R. \ Howell , author M. P. \ Meng \"u c , author K. J. \ Daun ,\ and\ author R. Siegel ,\ @noop title Thermal radiation heat transfer \ ( publisher CRC press ,\ year 2020 ) NoStop
2020
-
[3]
author author M. F. \ Modest \ and\ author S. Mazumder ,\ @noop title Radiative heat transfer \ ( publisher Academic press ,\ year 2021 ) NoStop
2021
-
[4]
author author J. R. \ Howell , author M. P. \ Meng \"u c ,\ and\ author K. J. \ Daun ,\ @noop title Thermal Radiation: An Introduction \ ( publisher CRC press ,\ year 2023 ) NoStop
2023
-
[5]
Zhao ,\ @noop title Thermal Radiation: From Macro to Nano \ ( publisher Cambridge University Press ,\ year 2024 ) NoStop
author author C. Zhao ,\ @noop title Thermal Radiation: From Macro to Nano \ ( publisher Cambridge University Press ,\ year 2024 ) NoStop
2024
-
[6]
Cheng , author J
author author C. Cheng , author J. Liu , author F. Wang ,\ and\ author C. Wang ,\ title title Photonic structures in multispectral camouflage: From static to dynamic technologies , \ https://www.sciencedirect.com/science/article/pii/S136970212500063X journal journal Mater. Today \ volume 85 ,\ pages 253--281 ( year 2025 ) NoStop
2025
-
[7]
author author S. Foteinopoulou , author G. C. R. \ Devarapu , author G. S. \ Subramania , author S. Krishna ,\ and\ author D. Wasserman ,\ title title Phonon-polaritonics: enabling powerful capabilities for infrared photonics , \ https://doi.org/10.1515/nanoph-2019-0232 journal journal Nanophotonics \ volume 8 ,\ pages 2129--2175 ( year 2019 ) NoStop
-
[8]
author author J. D. \ Caldwell , author L. Lindsay , author V. Giannini , author I. Vurgaftman , author T. L. \ Reinecke , author S. A. \ Maier ,\ and\ author O. J. \ Glembocki ,\ title title Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons , \ https://doi.org/10.1515/nanoph-2014-0003 journal journal Nanophotonics \ volume 4 ...
-
[9]
author author Z. Tong , author X. Yang , author T. Feng , author H. Bao ,\ and\ author X. Ruan ,\ title title First-principles predictions of temperature-dependent infrared dielectric function of polar materials by including four-phonon scattering and phonon frequency shift , \ https://link.aps.org/doi/10.1103/PhysRevB.101.125416 journal journal Phys. Rev...
-
[10]
author author C.-L. \ Zhou , author Z. Torbatian , author S.-H. \ Yang , author Y. Zhang , author H.-L. \ Yi , author M. Antezza , author D. Novko ,\ and\ author C.-W. \ Qiu ,\ title title Unconventional thermophotonic charge density wave , \ https://link.aps.org/doi/10.1103/PhysRevLett.133.066902 journal journal Phys. Rev. Lett. \ volume 133 ,\ pages 066...
-
[11]
Bao , author B
author author H. Bao , author B. Qiu , author Y. Zhang ,\ and\ author X. Ruan ,\ title title A first-principles molecular dynamics approach for predicting optical phonon lifetimes and far-infrared reflectance of polar materials , \ https://www.sciencedirect.com/science/article/pii/S0022407312002336 journal journal J. Quant. Spectrosc. Radiat. Transfer \ v...
2012
-
[12]
author author M. Simoncelli , author N. Marzari ,\ and\ author F. Mauri ,\ title title Wigner formulation of thermal transport in solids , \ https://link.aps.org/doi/10.1103/PhysRevX.12.041011 journal journal Phys. Rev. X \ volume 12 ,\ pages 041011 ( year 2022 ) NoStop
-
[13]
author author G. Coiana , author J. Lischner ,\ and\ author P. Tangney ,\ title title Breakdown of phonon band theory in MgO , \ https://link.aps.org/doi/10.1103/PhysRevB.109.014310 journal journal Phys. Rev. B \ volume 109 ,\ pages 014310 ( year 2024 ) NoStop
-
[14]
author author A. A. \ Maradudin \ and\ author R. F. \ Wallis ,\ title title Lattice anharmonicity and optical absorption in polar crystals. II . classical treatment in the linear approximation , \ https://link.aps.org/doi/10.1103/PhysRev.123.777 journal journal Phys. Rev. \ volume 123 ,\ pages 777--789 ( year 1961 ) NoStop
-
[15]
author author F. Gangemi , author A. Carati , author L. Galgani , author R. Gangemi ,\ and\ author A. Maiocchi ,\ title title Agreement of classical Kubo theory with the infrared dispersion curves n( ) of ionic crystals , \ https://dx.doi.org/10.1209/0295-5075/110/47003 journal journal Europhys. Lett. \ volume 110 ,\ pages 47003 ( year 2015 ) NoStop
-
[16]
Domingues , author A
author author G. Domingues , author A. M. \ Monthe , author S. Guévelou ,\ and\ author B. Rousseau ,\ title title Study by molecular dynamics of the influence of temperature and pressure on the optical properties of undoped 3C-SiC structures , \ https://www.sciencedirect.com/science/article/pii/S0022407317303448 journal journal J. Quant. Spectrosc. Radiat...
2018
-
[17]
author author W. Chen \ and\ author L.-S. \ Li ,\ title title The study of the optical phonon frequency of 3C-SiC by molecular dynamics simulations with deep neural network potential , \ https://doi.org/10.1063/5.0049464 journal journal J. Appl. Phys. \ volume 129 ,\ pages 244104 ( year 2021 ) NoStop
-
[18]
author author W.-Z. \ Yuan , author Y. Guo ,\ and\ author H.-L. \ Yi ,\ title title Consistency between the Green-Kubo formula and the lorentz model for predicting the infrared dielectric function of polar materials , \ https://link.aps.org/doi/10.1103/PhysRevB.111.184310 journal journal Phys. Rev. B \ volume 111 ,\ pages 184310 ( year 2025 ) NoStop
-
[19]
author author J. Behler ,\ title title Four generations of high-dimensional neural network potentials , \ https://doi.org/10.1021/acs.chemrev.0c00868 journal journal Chem. Rev. \ volume 121 ,\ pages 10037--10072 ( year 2021 ) NoStop
-
[20]
author author C.-Y. \ Wang , author S. Sharma , author E. K. U. \ Gross ,\ and\ author J. K. \ Dewhurst ,\ title title Dynamical born effective charges , \ https://link.aps.org/doi/10.1103/PhysRevB.106.L180303 journal journal Phys. Rev. B \ volume 106 ,\ pages L180303 ( year 2022 ) NoStop
-
[21]
author author P. Zhong , author D. Kim , author D. S. \ King ,\ and\ author B. Cheng ,\ title title Machine learning interatomic potential can infer electrical response , \ https://doi.org/10.1038/s41524-025-01911-z journal journal npj Comput. Mater. \ volume 11 ,\ pages 384 ( year 2025 ) NoStop
-
[22]
author author H. Luo , author L. Cao , author Z. Gao , author H. Ke ,\ and\ author Y. Zhou ,\ title title Nonlinear electronic polarizations and anharmonic phonon couplings in ferroelectric perovskite compounds , \ https://doi.org/10.1063/5.0299700 journal journal J. Appl. Phys. \ volume 138 ,\ pages 155102 ( year 2025 ) NoStop
-
[23]
author author Z. Deng , author C. Chen , author X.-G. \ Li ,\ and\ author S. P. \ Ong ,\ title title An electrostatic spectral neighbor analysis potential for lithium nitride , \ https://doi.org/10.1038/s41524-019-0212-1 journal journal npj Comput. Mater. \ volume 5 ,\ pages 75 ( year 2019 ) NoStop
-
[24]
author author Y. Wang , author M. Hu , author L. Xie ,\ and\ author J. He ,\ title title Orbit-lattice coupling leads to the intrinsic low thermal conductivity in mTe 4pt 0ex (m=Ge,Sn,Pb) thermoelectric materials , \ https://link.aps.org/doi/10.1103/PhysRevB.109.205204 journal journal Phys. Rev. B \ volume 109 ,\ pages 205204 ( year 2024 ) NoStop
-
[25]
author author P. Ghosez , author J.-P. \ Michenaud ,\ and\ author X. Gonze ,\ title title Dynamical atomic charges: The case of AB O _ 3 compounds , \ https://link.aps.org/doi/10.1103/PhysRevB.58.6224 journal journal Phys. Rev. B \ volume 58 ,\ pages 6224--6240 ( year 1998 ) NoStop
-
[26]
author author D. Bennett \ and\ author P. Ghosez ,\ title title Asymmetric dynamical charges in two-dimensional ferroelectrics , \ https://link.aps.org/doi/10.1103/PhysRevB.110.L041101 journal journal Phys. Rev. B \ volume 110 ,\ pages L041101 ( year 2024 ) NoStop
-
[27]
author author A. Pasquarello \ and\ author R. Car ,\ title title Dynamical charge tensors and infrared spectrum of amorphous SiO _ 2 , \ https://link.aps.org/doi/10.1103/PhysRevLett.79.1766 journal journal Phys. Rev. Lett. \ volume 79 ,\ pages 1766--1769 ( year 1997 ) NoStop
-
[28]
author author L. Giacomazzi , author N. S. \ Shcheblanov , author M. E. \ Povarnitsyn , author Y. Li , author A. c. v. \ Mavri c c , author B. Zupan c c i c c , author J. c. v. \ Grdadolnik ,\ and\ author A. Pasquarello ,\ title title Infrared spectra in amorphous alumina: A combined ab initio and experimental study , \ https://link.aps.org/doi/10.1103/Ph...
-
[29]
author author Z. Fan , author B. Tang , author E. Berger , author E. Berger , author E. Fransson , author K. Xu , author Z. Yan , author Z. Liu , author Z. Song , author H. Dong , author S. Chen , author L. Li , author Z. Wang , author Y. Zhu , author J. Wiktor ,\ and\ author P. Erhart ,\ title title qnep: A highly efficient neuroevolution potential with ...
-
[30]
author author C. Lee \ and\ author X. Gonze ,\ title title Dielectric constants and born effective charges of TiO _ 2 rutile , \ https://link.aps.org/doi/10.1103/PhysRevB.49.14730 journal journal Phys. Rev. B \ volume 49 ,\ pages 14730--14731 ( year 1994 ) NoStop
-
[31]
author author C. Schröder \ and\ author O. Steinhauser ,\ title title Using fit functions in computational dielectric spectroscopy , \ https://doi.org/10.1063/1.3432620 journal journal J. Chem. Phys. \ volume 132 ,\ pages 244109 ( year 2010 ) NoStop
-
[32]
author author J. S. \ Toll ,\ title title Causality and the dispersion relation: Logical foundations , \ https://link.aps.org/doi/10.1103/PhysRev.104.1760 journal journal Phys. Rev. \ volume 104 ,\ pages 1760--1770 ( year 1956 ) NoStop
-
[33]
author author F. m. c. \ Gervais \ and\ author B. Piriou ,\ title title Temperature dependence of transverse- and longitudinal-optic modes in Ti O _ 2 (rutile) , \ https://link.aps.org/doi/10.1103/PhysRevB.10.1642 journal journal Phys. Rev. B \ volume 10 ,\ pages 1642--1654 ( year 1974 ) NoStop
-
[34]
author author D. Kim \ and\ author B. Cheng ,\ title title Long-range electrostatics for machine learning interatomic potentials is easier than we thought , \ https://doi.org/10.1063/5.0316886 journal journal J. Chem. Phys. \ volume 164 ,\ pages 060901 ( year 2026 ) NoStop
-
[35]
author author P. Giannozzi , author O. Baseggio , author P. Bonfà , author D. Brunato , author R. Car , author I. Carnimeo , author C. Cavazzoni , author S. de Gironcoli , author P. Delugas , author F. Ferrari Ruffino , author A. Ferretti , author N. Marzari , author I. Timrov , author A. Urru ,\ and\ author S. Baroni ,\ title title Quantum ESPRESSO towar...
-
[36]
author author J. P. \ Perdew \ and\ author A. Zunger ,\ title title Self-interaction correction to density-functional approximations for many-electron systems , \ https://link.aps.org/doi/10.1103/PhysRevB.23.5048 journal journal Phys. Rev. B \ volume 23 ,\ pages 5048--5079 ( year 1981 ) NoStop
-
[37]
author author K. Xu , author H. Bu , author S. Pan , author E. Lindgren , author Y. Wu , author Y. Wang , author J. Liu , author K. Song , author B. Xu , author Y. Li , author T. Hainer , author L. Svensson , author J. Wiktor , author R. Zhao , author H. Huang , author C. Qian , author S. Zhang , author Z. Zeng , author B. Zhang , author B. Tang , author ...
-
[38]
author author J. Eastwood , author R. Hockney ,\ and\ author D. Lawrence ,\ title title P3M3DP —the three-dimensional periodic particle-particle/ particle-mesh program , \ https://www.sciencedirect.com/science/article/pii/0010465580900521 journal journal Comp. Phys. Comm. \ volume 19 ,\ pages 215--261 ( year 1980 ) NoStop
-
[39]
author author M. Schubert ,\ title Infrared ellipsometry on semiconductor layer structures: Phonons, plasmons, and polaritons , \ \ ( publisher Springer ,\ address Berlin, Heidelberg ,\ year 2004 )\ pp.\ pages 31--43 NoStop
2004
-
[40]
author author T. Amano , author T. Yamazaki , author R. Akashi , author T. Tadano ,\ and\ author S. Tsuneyuki ,\ title title Lattice dielectric properties of rutile TiO _ 2 : First-principles anharmonic self-consistent phonon study , \ https://link.aps.org/doi/10.1103/PhysRevB.107.094305 journal journal Phys. Rev. B \ volume 107 ,\ pages 094305 ( year 202...
-
[41]
author author F. Gervais ,\ title title Effective charges in binary and ternary oxide compounds , \ https://doi.org/https://doi.org/10.1016/0038-1098(76)91451-4 journal journal Solid State Commun. \ volume 18 ,\ pages 191--198 ( year 1976 ) NoStop
-
[42]
author author K. Wakamura ,\ title title Thermal expansion and anharmonic phonon-phonon interaction effects on an effective charge in GaAs and KCl , \ https://doi.org/https://doi.org/10.1016/0022-3697(93)90274-U journal journal J. Phys. Chem. Solids \ volume 54 ,\ pages 387--395 ( year 1993 ) NoStop
-
[43]
author author D. Olego \ and\ author M. Cardona ,\ title title Temperature dependence of the optical phonons and transverse effective charge in 3C -SiC , \ https://doi.org/10.1103/PhysRevB.25.3889 journal journal Phys. Rev. B \ volume 25 ,\ pages 3889--3896 ( year 1982 ) NoStop
-
[44]
author author J. A. \ Thomas , author J. E. \ Turney , author R. M. \ Iutzi , author C. H. \ Amon ,\ and\ author A. J. H. \ McGaughey ,\ title title Predicting phonon dispersion relations and lifetimes from the spectral energy density , \ https://link.aps.org/doi/10.1103/PhysRevB.81.081411 journal journal Phys. Rev. B \ volume 81 ,\ pages 081411 ( year 20...
-
[45]
author author J. G. \ Traylor , author H. G. \ Smith , author R. M. \ Nicklow ,\ and\ author M. K. \ Wilkinson ,\ title title Lattice dynamics of rutile , \ https://link.aps.org/doi/10.1103/PhysRevB.3.3457 journal journal Phys. Rev. B \ volume 3 ,\ pages 3457--3472 ( year 1971 ) NoStop
-
[46]
author author R. A. \ Parker ,\ title title Static dielectric constant of rutile (Ti O _ 2 ) , 1.6-1060 ^ K , \ https://link.aps.org/doi/10.1103/PhysRev.124.1719 journal journal Phys. Rev. \ volume 124 ,\ pages 1719--1722 ( year 1961 ) NoStop
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.