Properties of Materials

Biogenic and bio-inspired materials

Living organisms produce a wide range of materials, often revealing unique shapes, morphologies, structures, and functionality. Examples range from inorganic materials, such as calcium carbonates and phosphates used in, e.g., shells, bones, and teeth, to organic materials such as chitin, a polysaccharide used in the exoskeletons of arthropods, or a molecular solid of guanine, formed by various organisms for vision or for camouflage.

Bio-inspired materials generally attempt to learn from nature's achievements, by incorporating natural components or motifs in order to achieve ease of fabrication and/or desired functionality. These materials often exhibit unique mechanical, electrical, optical, or even magnetic properties, leading to novel applications.

In our work, we attempt to understand the unique order and structure in both biogenic and bio-inspired materials, and to discover novel properties and new structure-property relations. This is typically achieved by comparing first-principles calculations to the results of various microscopy and spectroscopy tools.

For an overview of organic crystals and their optical function in Biology, see:

  • L. Addadi, L. Kronik, L. Leiserowitz, D. Oron, and S. Weiner, “Organic Crystals and Optical Functions in Biology: Knowns and Unknowns”, Adv. Materials. 36, 2408060 (2024).

Some recent research achievements include:

Understanding polymorphism, structure, and nucleation of cholesterol·H2O, a pathological biological material, see: 

  • M. Shepelenko, A. Hirsch, N. Varsano, F. Beghi, L. Addadi, L. Kronik, and L. Leiserowitz, “Polymorphism, Structure, and Nucleation of Cholesterol·H2O at Aqueous Interfaces and Pathological Media: a Computational Perspective”, J. Am. Chem. Soc. 144, 5304 (2022).

Understanding high-refractive index birefringence in bio-inspired xanthine-derivative based materials, see: 

  • A. Niazov-Elkan, M. Shepelenko, L. Alus, M. Kazes, K. Rechav, G. Leitus, A.-E. Kossoy, Y. Feldman, L. Kronik, P. G. Vekilov, and D. Oron, “Surface-guided crystallization of xanthine derivatives for optical metamaterial applications”, Adv. Mater. 36, 2306996 (2024).

Discovering the crystal structure of biogenic xanthine crystals, see:

  • M. Ifliand, L. Houben, M. Shepelenko, Y. Feldman, A. E. Kossoy, O. Friedman, M. Hildebrand, L. Addadi, L. Leiserowitz, L. Kronik, “Discovering the crystal structure of biogenic xanthine crystals”, Cryst. Growth & Design 25, 7524-7536 (2025).

Showing that pH Variations Enable Guanine Crystal Formation within Iridosomes, see:

  • Z. Eyal, A. Gorelick-Ashkenazi, R. Deis, Y. Barzilay, Y. Broder, A. P. Kellum, N. Varsano, M. Hartstein, A. Sorrentino, I. Kaplan-Ashiri, K. Rechav, R. Metzler, L. Houben, L. Kronik, P. Rez, and D. Gur, “pH Variations Enable Guanine Crystal Formation within Iridosomes”, Nature Chem. Biol. (2025).

Understanding Guanine Crystallization by Particle Attachment, see:

Halide Perovskites

Halide perovskites (HaPs) are crystals with the structural formula ABX3, in which A is an organic or inorganic cation, B is a metal cation, and X is a halide anion. While known for a long time, in the last decade HaPs have emerged as extremely promising low cost yet high efficiency semiconducting materials for solar energy and other photovoltaic applications. It is thus of fundamental importance to reveal physical and chemical phenomena that govern the behavior of these materials. A preponderance of studies have suggested that in HaPs a variety of large structural dynamic effects, beyond small harmonic vibrations, arise already at room temperature. Our research focuses on the theoretical understanding and prediction of such effects, with an emphasis on their influence on defect properties.

Selected overviews include:

  • General overview:
    • T. M. Brenner, D. A. Egger, L. Kronik, G. Hodes, D. Cahen “Hybrid organic–inorganic perovskites: low-cost semiconductors with intriguing charge transport properties”, Nature Reviews Materials 1, 15007 (2016).
  • Overview of dynamic effects:
    • D. A. Egger, A. M. Rappe, and L. Kronik, “Hybrid Organic-Inorganic Perovskites on the Move”, Acct. Chem. Research (Special Issue on Lead-Halide Perovskites for Solar Energy Conversion), Acc. Chem. Res. 49, 573 (2016).
  • Overview of unique optoelectronic properties of halide perovskites:
    • D. A. Egger, A. Bera, D. Cahen, G. Hodes, T. Kirchartz, L. Kronik, R. Lovrincic, A. M. Rappe, D. R. Reichman, and O. Yaffe, “What remains unexplained about the optoelectronic properties of halide perovskites?”, Adv. Mater. 30, 1800691 (2018).
  • A Broader Photoelectrochemistry Perspective of HaPs 
    • Z. Xu, R. A. Kerner, L. Kronik, B. P. Rand, “Beyond Ion Migration in Metal Halide Perovskites: Towards a Broader Photoelectrochemistry Perspective”, ACS Energy Lett. 9, 4645 (2024).

Selected research achievements include:

  • F. P. Delgado, F. Simões, L. Kronik, W. Kaiser, and D. A. Egger, “Machine-Learning Force Fields Reveal Shallow Electronic States on Dynamic Halide Perovskite Surfaces”, ACS Energy Lett. 10, 3367-3374 (2025).
  • R. A. Kerner, A. V. Cohen, Z. Xu, A. R. Kirmani, S. Y. Park, S. P. Harvey, J. P. Murphy, R. C. Cawthorn, N. C. Giebink, J. M. Luther, K. Zhu, J. J. Berry, L. Kronik, and B. P. Rand, “Electrochemical Doping of Halide Perovskites by Noble Metal Interstitial Cations”, Adv. Materials 35, 2302206 (2023).
  • D. Shin, F. Zu, A. V. Cohen, Y. Yi, L. Kronik, and N. Koch,”Mechanism and time-scales of reversible p-doping of methylammonium lead triiodide by oxygen”, Adv. Materials 33, 2100211 (2021).
  • A. V. Cohen, D. A. Egger, A. M. Rappe, and L. Kronik, “Breakdown of the static picture of defect energetics in halide perovskites: the case of the Br vacancy in CsPbBr3”, J. Phys. Chem. Lett. 10, 4490 (2019).
  • O. Yaffe, Y. Guo, L. Z. Tan, D. A. Egger, T. Hull, C. C. Stoumpos, F. Zheng, T. F. Heinz, L. Kronik, M. G. Kanatzidis, J. S Owen, A. M. Rappe, M. A. Pimenta, and L. E. Brus, “Local polar fluctuations in lead halide perovskite crystals”, Phys. Rev. Lett. 118, 136001 (2017).

Two-dimensional materials

Two-dimensional (2d) materials are crystalline solids that are only one or few atomic layers thick. These materials often exhibit unique mechanical, electronic, and optical properties. This has many potential applications and also raises basic science questions as to how these unique properties emerge. 

Recent highlights of our work include: 

Development and applications of anisotropic interlayer force fields for van homogeneous and heterogeneous 2d-layer interfaces:

  •  For a recent overview see:
  • For recent research articles see:
    • W. Jiang, R. Sofer, X. Gao, L. Kronik, O. Hod, M. Urbakh, and W. Ouyang, “Anisotropic Interlayer Force Field for Heterogeneous Interfaces of Graphene and h-BN with Transition Metal Dichalcogenides”, J. Phys. Chem. C. 129, 1417–1427 (2025).
    • W. Jiang, R. Sofer, X. Gao, A. Tkatchenko, L. Kronik, W. Ouyang, M. Urbakh, O. Hod, “Anisotropic Interlayer Force Field for Group-VI Transition Metal Dichalcogenides”, J. Phys.Chem. A 127 ,9820 (2023). Special Issue in honor of Prof. Gustavo Scuseria.

Understanding cumulative polarization in multi-layered interfacial ferroelectrics:

  •  W. Cao, S. Deb, M. Vizner Stern, N. Raab, M. Urbakh, O. Hod, L. Kronik, M. Ben Shalom, “Polarization Saturation in Multi-layered Interfacial Ferroelectrics”, Adv. Mater. 36, 2400750 (2024).
  •  S. S. Atri, W. Cao, B. Alon, N. Roy, M. Vizner Stern, V. Falko, M. Goldstein, L. Kronik, M. Urbakh, O. Hod, M. Ben Shalom, “Spontaneous Electric Polarization in Graphene Polytypes”, Adv. Phys. Research 3, 2300095 (2024).
  • S. Deb, W. Cao, N. Raab, K. Watanabe, T. Taniguchi, M. Goldstein, L. Kronik, M. Urbakh, O. Hod, and M. Ben Shalom, “Cumulative Polarization in Conductive Interfacial Ferroelectrics”, Nature 612, 465 (2022).

Unique structure-property relations in 2d materials:

  • A. Champagne, M. Camarasa-Gómez, F. Ricci, L. Kronik, and J. B. Neaton, “Strongly-bound excitons and anisotropic linear absorption in monolayer graphullerene”, Nano Lett. 24, 7033 (2024).
  • Y.-C. Leem, Z. Fang, C. Lee, N.-Y. Kim, W. Liu, S.-P. Cho, C. Kim, Y. Wang, Z. Ji, L. Kronik, A. M. Rappe, S.-Y. Yim, R. Agarwal, “Optically-triggered emergent mesostructures in monolayer WS2”, Nano Lett. 24, 5395 (2024).

Methods for accurate prediction of electronic and optical properties in 2d materials:

  • F. Florio, M. Camarasa-Gómez, G. Ohad, D. Naveh, L. Kronik, and A. Ramasubramaniam, “Resolving contradictory estimates of bandgaps of bulk PdSe2: A Wannier-localized optimally-tuned screened range-separated hybrid density functional theory study”, Appl. Phys. Lett. 126, 143101 (2025).
  • M. Camarasa-Gómez, S. E. Gant, G. Ohad, J. B. Neaton, A. Ramasubramaniam, L. Kronik, “Electronic and Optical Excitations in van der Waals Materials from a Non-Empirical Wannier-Localized Optimally-Tuned Screened Range-Separated Hybrid Functional”, npj Comp.Mater. 10, 288 (2024).
  • M. Camarasa-Gómez, A. Ramasubramaniam, J. B. Neaton, L. Kronik, “Transferable screened range-separated hybrid functionals for electronic and optical properties of van der Waals materials”, Phys. Rev. Materials 7, 104001 (2023).

Molecular Spintronics

Spintronics is a field of electronics that uses the fundamental property of an electron spin, in addition to its charge, in order to store and/or process and/or transmit information. Molecular electronics is a field of electronics that uses single molecules as building blocks for electronic components like transistors, diodes, and wires. Molecular spintronics joins these two fields in that it used single molecules as building blocks for spintronic devices and phenomena.

Our research in molecular spintronics focuses mainly on understanding chirality-induced spin selectivity, an umbrella term that defines a wide range of phenomena in which the chirality of molecular species imparts significant spin selectivity to various electron processes.

For an overview, see:

  • F. Evers, A. Aharony, N. Bar-Gill, O. Entin-Wohlman, P. Hedegård, O. Hod, P. Jelinek, G. Kamieniarz, M. Lemeshko, K. Michaeli, V. Mujica, R. Naaman, Y. Paltiel, S. Refaely-Abramson, O. Tal, J. Thijssen, M. Thoss, J. M. van Ruitenbeek, L. Venkataraman, D. H. Waldeck, B. Yan, and L. Kronik, “Theory of Chirality Induced Spin Selectivity: Progress and Challenges”, Adv. Materials, 34 2106629 (2022).

For recent research highlights, see:

  • A. K. Mondal, N. Brown, S. Mishra, P. Makam, D. Wing, Y. Wiesenfeld, G. Leitus, L. J. W. Shimon, R. Carmieli, D. Ehre, G. Kamieniarz, J. Fransson, O. Hod, L. Kronik, E. Gazit, and R. Naaman, “Long-Range Spin-Selective Transport in Chiral Metal-Organic Crystals with Temperature-Activated Magnetization”, ACS Nano 14, 16624 (2020).
  • K. Banerjee-Ghosh, O. Ben Dor, F. Tassinari, E. Capua, S. Yochelis, A. Capua, S.-H. Yang, S. S. P. Parkin, S. Sarkar, L. Kronik, L. T. Baczewski, R. Naaman, and Y. Paltiel, “Separation of enantiomers by their enantiospecific interaction with achiral magnetic substrates”, Science 360, 1331 (2018). Highlighted by Chemical & Engineering News and Physics Today​​​​​​​.

Porphyrins and phthalocyanines

Porphyrins, phthalocyanines and their numerous analogues and derivatives are organic macrocycles of outstanding importance in a wide range of fields, from chemistry and materials science, through electronics and spintronics, to biology and medicine. Among many other things, they paint blood red (heme), leaves green (chlorophyll), and jeans blue (copper phthalocyanine). Our research is aimed at a fundamental understanding of their unique electronic structure and optical properties, especially but not only in the solid state, using advanced density functional theory approaches.

Some recent research achievements include:

  • Structure, bonding, and reactivity trends in subphthalocyanines:
  • Identification of a new polymorph of copper phthalocyanine:
    • I. Biran, L. Houben, H. Weismann, M. Hildebrand, L. Kronik, and B. Rybtchinski, “Real-space crystallography by low-dose focal-series TEM imaging of organic materials with near-atomic resolution”, Adv. Materials 34, 2202088 (2022).
       
  • Electronic and magnetic coupling in iron corroles:
    • A. Mizrahi, S. Bhowmik, A. Manna, W. Sinha, A. Kumar, M. Saphier, A. Mahammed, M. Patra, N. Fridman, I. Zilbermann, L. Kronik, and Z. Gross, “Electronic Coupling and Electrocatalysis in Redox Active Fused Iron Corrole”, Inorg. Chem. 61, 20725 (2022).​​​​​​​