Details of the Researcher

PHOTO

Sau Kartik
Section
Advanced Institute for Materials Research
Job title
Senior Assistant Professor
Profile

I am a computational materials scientist dedicated to advancing sustainable energy technologies through the discovery and design of novel functional materials. My research integrates quantum mechanical calculations, molecular dynamics/Monte Carlo simulations, and data-driven machine learning approaches to understand structure-property relationships at the atomic scale. At WPI-AIMR, Tohoku University, I lead research projects focused on developing next-generation materials for energy storage, conversion, and efficiency applications. My work contributes to the fundamental understanding of material behavior while addressing critical challenges in renewable energy technologies.

 

Research areas include: Molecular Dynamics (MD) Simulation, Monte Carlo (MC) Simulation, Density Functional Theory (DFT), Machine Learning (ML) for Materials Screening, Fast Ion Conductors, Caloric Materials, Hydrogen Storage Materials, and Quantum Chemistry.

Research History 6

  • 2026 - Present
    Tohoku University　WPI-AIMR (Advanced Institute for Materials Research)　Senior Assistant Professor

  • 2024 - 2026
    Tohoku University　WPI-AIMR (Advanced Institute for Materials Research)　Specially Appointed Senior Assistant Professor

  • 2023 - 2024
    AIST (National Institute of Advanced Industrial Science and Technology)　MathAM-OIL　Post-doctoral Researcher

  • 2021 - 2023
    Tohoku University　WPI-AIMR (Advanced Institute for Materials Research)　JSPS Post-doctoral Researcher

  • 2021/01 - 2021/04
    AIST Kansai (National Institute of Advanced Industrial Science and Technology)　Post-doctoral Researcher

  • 2017 - 2021
    AIST (National Institute of Advanced Industrial Science and Technology)　MathAM-OIL　Post-doctoral Researcher

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Education 3

  • IIT Guwahati　Department of Physics　Ph.D. in Physics

    2013 - 2017

  • IIT Guwahati　Department of Physics　M.Sc. in Physics

    2009 - 2011

  • Calcutta University　Department of Physics　B.Sc. in Physics

    2006 - 2009

Research Interests 7

  • Monte Carlo (MC) Simulation

  • Quantum Chemistry / Electronic structure

  • Machine Learning for materials discovery

  • Molecular Dynamics (MD) Simulation

  • Hydrogen storage materials

  • Caloric materials / Barocaloric cooling

  • All-solid-state batteries

Research Areas 1

  • Nanotechnology/Materials / Functional solid-state chemistry / fast ion conductors, all-solid-state batteries, molecular dynamics simulation

Papers 27

  1. Hybrid sampling approach to machine-learning potentials for gas adsorption: Hydrogen adsorption in MOF-303

    Kartik Sau, Ikutaro Hamada, Tamio Ikeshoji, Yiming Lu, Susmita Roy, Shohichi Furukawa, Linda Zhang, Hung Ba Tran, Takahiro Kondo, Hao Li, Shin-ichi Orimo

    2026/02/04

    Publisher: American Chemical Society (ACS)

    DOI： 10.26434/chemrxiv-2025-dkt8s/v2 　

  2. Visualizing Concerted Ion Migration of Superionic Conductors via Directed Graphs

    Ryuhei Sato, Yasunobu Ando, Kartik Sau, Yasushi Shibuta

    Chemistry of Materials　38　(1)　287-295　2025/12/12

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.chemmater.5c02374 　

    ISSN： 0897-4756

    eISSN： 1520-5002

  3. Surface melting–driven hydrogen absorption for high-pressure polyhydride synthesis

    Ryuhei Sato, Lewis J. Conway, Di Zhang, Chris J. Pickard, Kazuto Akagi, Kartik Sau, Hao Li, Shin-ichi Orimo

    Proceedings of the National Academy of Sciences　122　(22)　2025/05/29

    Publisher: Proceedings of the National Academy of Sciences

    DOI： 10.1073/pnas.2413480122 　

    ISSN： 0027-8424

    eISSN： 1091-6490

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    The synthesis of new polyhydrides with high superconducting T c is challenging owing to the high pressures and temperatures required. In this study, we used machine-learning potential molecular dynamics simulations to investigate the initial stage of polyhydride formation in calcium hydrides. Upon contact with high-pressure H 2 , the surface of CaH 2 melts, leading to CaH 4 formation. This surface melting proceeds via CaH 4 liquid phase as an intermediate state. High pressure reduces not only the hydrogenation (CaH 2 (s) + H 2 (l) ↔ CaH 4 (s)) enthalpy but also the enthalpy for liquid polyhydride formation (CaH 2 (s) + H 2 (l) ↔ CaH 4 (l)). Consequently, this surface melting process becomes more favorable than the fusion of the polyhydride bulk. Thus, high pressure not only shifts the equilibrium toward the polyhydride product but also lowers the activation energy, thereby promoting the hydrogenation reaction. From these thermodynamic insights, we propose structure-search criteria for polyhydride synthesis that are both computationally effective and experimentally relevant. These criteria are based on bulk properties, such as polyhydride (product) melting temperature and pressure-dependent hydrogenation enthalpy, readily determined through supplementary calculations during structure prediction workflows.

  4. Unlocking the secrets of ideal fast ion conductors for all-solid-state batteries

    Kartik Sau, Shigeyuki Takagi, Tamio Ikeshoji, Kazuaki Kisu, Ryuhei Sato, Egon Campos dos Santos, Hao Li, Rana Mohtadi, Shin-ichi Orimo

    Communications Materials　5　(1)　2024/07/19

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1038/s43246-024-00550-z 　

    eISSN： 2662-4443

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    Abstract All-solid-state batteries (ASSBs) are promising alternatives to conventional lithium-ion batteries. ASSBs consist of solid-fast-ion-conducting electrolytes and electrodes that offer improved energy density, battery safety, specific power, and fast-charging capability. Despite decades of intensive research, only a few have high ionic conductivity at ambient temperature. Developing fast ion-conducting materials requires both synthesis of high-conducting materials and a fundamental understanding of ion transport mechanisms. However, this is challenging due to wide variations of the ionic conductivity, even within the same class of materials, indicating the strong influence of structural modifications on ion transport. This Review discusses three selected material classes, namely layered oxides, polyhedral connections, and cluster anion types, as promising fast ion conductors. Emphasis is placed on the inherent challenges and the role of the framework structure on mobile ion conduction. We elucidate strategies to address these challenges by leveraging theoretical frameworks and insights from materials science.

  5. Colossal Reversible Barocaloric Effects in a Plastic Crystal Mediated by Lattice Vibrations and Ion Diffusion

    Ming Zeng, Carlos Escorihuela‐Sayalero, Tamio Ikeshoji, Shigeyuki Takagi, Sangryun Kim, Shin‐ichi Orimo, María Barrio, Josep‐Lluís Tamarit, Pol Lloveras, Claudio Cazorla, Kartik Sau

    Advanced Science　11　(26)　2024/05/05

    Publisher: Wiley

    DOI： 10.1002/advs.202306488 　

    ISSN： 2198-3844

    eISSN： 2198-3844

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    Abstract Solid‐state methods for cooling and heating promise a sustainable alternative to current compression cycles of greenhouse gases and inefficient fuel‐burning heaters. Barocaloric effects (BCE) driven by hydrostatic pressure (p) are especially encouraging in terms of large adiabatic temperature changes (|ΔT| ≈ 10 K) and isothermal entropy changes (|ΔS| ≈ 100 J K−1 kg−1). However, BCE typically require large pressure shifts due to irreversibility issues, and sizeable |ΔT| and |ΔS| seldom are realized in a same material. Here, the existence of colossal and reversible BCE in LiCB11H12 is demonstrated near its order‐disorder phase transition at ≈380 K. Specifically, for Δp ≈ 0.23 (0.10) GPa, |ΔSrev| = 280 (200) J K−1 kg−1 and |ΔTrev| = 32 (10) K are measured, which individually rival with state‐of‐the‐art BCE figures. Furthermore, pressure shifts of the order of 0.1 GPa yield huge reversible barocaloric strengths of ≈2 J K−1 kg−1 MPa−1. Molecular dynamics simulations are performed to quantify the role of lattice vibrations, molecular reorientations, and ion diffusion on the disclosed BCE. Interestingly, lattice vibrations are found to contribute the most to |ΔS| while the diffusion of lithium ions, despite adding up only slightly to the entropy change, is crucial in enabling the molecular order–disorder phase transition.

  6. Landscape-Sketch-Step: An AI/ML-Based Metaheuristic for Surrogate Optimization Problems

    R Monteiro, K Sau

    2023/09

  7. Explore the Ionic Conductivity Trends on B12H12 Divalent Closo-Type Complex Hydride Electrolytes

    Egon Campos dos Santos, Ryuhei Sato, Kazuaki Kisu, Kartik Sau, Xue Jia, Fangling Yang, Shin-ichi Orimo, Hao Li

    Chemistry of Materials　35　(15)　5996-6004　2023/07/26

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.chemmater.3c00975 　

    ISSN： 0897-4756

    eISSN： 1520-5002

  8. Topological Data analysis of Ion Migration Mechanism

    Ryuhei Sato, Kazuto Akagi, Shigeyuki Takagi, Kartik Sau, Kazuaki Kisu, Hao Li, Shin-ichi Orimo

    The Journal of Chemical Physics　158　(14)　2023/04/13

    Publisher: AIP Publishing

    DOI： 10.1063/5.0143387 　

    ISSN： 0021-9606

    eISSN： 1089-7690

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    Topological data analysis based on persistent homology has been applied to the molecular dynamics simulation for the fast ion-conducting phase (α-phase) of AgI to show its effectiveness on the ion migration mechanism analysis. Time-averaged persistence diagrams of α-AgI, which quantitatively record the shape and size of the ring structures in the given atomic configurations, clearly showed the emergence of the four-membered rings formed by two Ag and two I ions at high temperatures. They were identified as common structures during the Ag ion migration. The averaged potential energy change due to the deformation of the four-membered ring during Ag migration agrees well with the activation energy calculated from the conductivity Arrhenius plot. The concerted motion of two Ag ions via the four-membered ring was also successfully extracted from molecular dynamics simulations by our approach, providing new insight into the specific mechanism of the concerted motion.

  9. The role of cation size in the ordered–disordered phase transition temperature and cation hopping mechanism based on LiCB11H12

    Kartik Sau, Shigeyuki Takagi, Tamio Ikeshoji, Kazuaki Kisu, Ryuhei Sato, Shin-ichi Orimo

    Materials Advances　4　(10)　2269-2280　2023

    Publisher: Royal Society of Chemistry (RSC)

    DOI： 10.1039/d2ma00936f 　

    eISSN： 2633-5409

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    The ordered–disordered transition temperature is reduced significantly with increasing cationic sizes. A possible principle for creating better ion-conducting materials is to have smaller cations in a larger unit cell.

  10. Particle size and temperature effects on thermal conductivity of aqueous Ag nanofluids: modelling and simulations using classical molecular dynamics

    Sakti Pada Shit, N. K. Ghosh, Sudipta Pal, Kartik Sau

    The European Physical Journal D　76　(12)　2022/12/09

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1140/epjd/s10053-022-00561-w 　

    ISSN： 1434-6060

    eISSN： 1434-6079

  11. Enhanced thermophysical properties of water-based single and hybrid metallic nanofluids: Insights from Equilibrium Molecular Dynamics

    Sakti Pada Shit, Sudipta Pal, N.K. Ghosh, Kartik Sau

    Chemical Thermodynamics and Thermal Analysis　8　100096-100096　2022/12

    Publisher: Elsevier BV

    DOI： 10.1016/j.ctta.2022.100096 　

    ISSN： 2667-3126

  12. Insights of cationic diffusion in nickel-based honeycomb layered tellurates using molecular dynamics simulation

    Kartik Sau, Tamio Ikeshoji

    Solid State Ionics　383　115982-115982　2022/10

    Publisher: Elsevier BV

    DOI： 10.1016/j.ssi.2022.115982 　

    ISSN： 0167-2738

  13. Ring mechanism of fast Na+ ion transport in Na2⁢LiFeTeO6: Insight from molecular dynamics simulation

    Kartik Sau, Tamio Ikeshoji

    Physical Review Materials　6　(4)　2022/04/29

    Publisher: American Physical Society (APS)

    DOI： 10.1103/physrevmaterials.6.045406 　

    eISSN： 2475-9953

  14. Fast divalent conduction in MB12H12·12H2O (M = Zn, Mg) complex hydrides: effects of rapid crystal water exchange and application for solid-state electrolytes

    Kazuaki Kisu, Arunkumar Dorai, Sangryun Kim, Riku Hamada, Akichika Kumatani, Yoshiko Horiguchi, Ryuhei Sato, Kartik Sau, Shigeyuki Takagi, Shin-ichi Orimo

    Journal of Materials Chemistry A　10　(46)　24877-24887　2022

    Publisher: Royal Society of Chemistry (RSC)

    DOI： 10.1039/d2ta06060d 　

    ISSN： 2050-7488

    eISSN： 2050-7496

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    Water molecules are exchanged in the crystal structure, which imparts a high divalent conductivity to hydrated complex hydrides. MB12H12·12H2O (M = Zn or Mg) exhibits exceptional conductivities higher than those of less-hydrated complex hydrides.

  15. Thermophysical properties of graphene and hexagonal boron nitride nanofluids: A comparative study by molecular dynamics

    Sakti Pada Shit, Sudipta Pal, N.K. Ghosh, Kartik Sau

    Journal of Molecular Structure　1239　130525-130525　2021/09

    Publisher: Elsevier BV

    DOI： 10.1016/j.molstruc.2021.130525 　

    ISSN： 0022-2860

  16. Mixed alkali-ion transport and storage in atomic-disordered honeycomb layered NaKNi2TeO6

    Titus Masese, Yoshinobu Miyazaki, Josef Rizell, Godwill Mbiti Kanyolo, Chih-Yao Chen, Hiroki Ubukata, Keigo Kubota, Kartik Sau, Tamio Ikeshoji, Zhen-Dong Huang, Kazuki Yoshii, Teruo Takahashi, Miyu Ito, Hiroshi Senoh, Jinkwang Hwang, Abbas Alshehabi, Kazuhiko Matsumoto, Toshiyuki Matsunaga, Kotaro Fujii, Masatomo Yashima, Masahiro Shikano, Cédric Tassel, Hiroshi Kageyama, Yoshiharu Uchimoto, Rika Hagiwara, Tomohiro Saito

    Nature Communications　12　(1)　2021/08/02

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1038/s41467-021-24694-5 　

    eISSN： 2041-1723

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    Abstract Honeycomb layered oxides constitute an emerging class of materials that show interesting physicochemical and electrochemical properties. However, the development of these materials is still limited. Here, we report the combined use of alkali atoms (Na and K) to produce a mixed-alkali honeycomb layered oxide material, namely, NaKNi 2 TeO 6 . Via transmission electron microscopy measurements, we reveal the local atomic structural disorders characterised by aperiodic stacking and incoherency in the alternating arrangement of Na and K atoms. We also investigate the possibility of mixed electrochemical transport and storage of Na + and K + ions in NaKNi 2 TeO 6 . In particular, we report an average discharge cell voltage of about 4 V and a specific capacity of around 80 mAh g –1 at low specific currents (i.e., < 10 mA g –1 ) when a NaKNi 2 TeO 6 -based positive electrode is combined with a room-temperature NaK liquid alloy negative electrode using an ionic liquid-based electrolyte solution. These results represent a step towards the use of tailored cathode active materials for “dendrite-free” electrochemical energy storage systems exploiting room-temperature liquid alkali metal alloy materials.

  17. Colossal barocaloric effects in the complex hydride Li$$_{2}$$B$$_{12}$$H$$_{12}$$

    Kartik Sau, Tamio Ikeshoji, Shigeyuki Takagi, Shin-ichi Orimo, Daniel Errandonea, Dewei Chu, Claudio Cazorla

    Scientific Reports　11　(1)　2021/06/07

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1038/s41598-021-91123-4 　

    eISSN： 2045-2322

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    Abstract Traditional refrigeration technologies based on compression cycles of greenhouse gases pose serious threats to the environment and cannot be downscaled to electronic device dimensions. Solid-state cooling exploits the thermal response of caloric materials to changes in the applied external fields (i.e., magnetic, electric and/or mechanical stress) and represents a promising alternative to current refrigeration methods. However, most of the caloric materials known to date present relatively small adiabatic temperature changes ($$|\Delta T| \sim 1$$ to 10 K) and/or limiting irreversibility issues resulting from significant phase-transition hysteresis. Here, we predict by using molecular dynamics simulations the existence of colossal barocaloric effects induced by pressure (isothermal entropy changes of $$|\Delta S| \sim 100$$ J K$$^{-1}$$ kg$$^{-1}$$) in the energy material Li$$_{2}$$B$$_{12}$$H$$_{12}$$. Specifically, we estimate $$|\Delta S| = 367$$ J K$$^{-1}$$ kg$$^{-1}$$ and $$|\Delta T| = 43$$ K for a small pressure shift of P = 0.1 GPa at $$T = 480$$ K. The disclosed colossal barocaloric effects are originated by a fairly reversible order–disorder phase transformation involving coexistence of Li$$^{+}$$ diffusion and (BH)$$_{12}^{-2}$$ reorientational motion at high temperatures.

  18. Comparative Molecular Dynamics Study of the Roles of Anion–Cation and Cation–Cation Correlation in Cation Diffusion in Li 2 B 12 H 12 and LiCB 11 H 12

    Kartik Sau, Tamio Ikeshoji, Sangryun Kim, Shigeyuki Takagi, Shin-ichi Orimo

    Chemistry of Materials　33　(7)　2357-2369　2021/03/19

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.chemmater.0c04473 　

    ISSN： 0897-4756

    eISSN： 1520-5002

  19. Origin of Fast Ion Conduction in Na3PS4: Insight from Molecular Dynamics Study

    Kartik Sau, Tamio Ikeshoji

    The Journal of Physical Chemistry C　124　(38)　20671-20681　2020/08/28

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.jpcc.0c04476 　

    ISSN： 1932-7447

    eISSN： 1932-7455

  20. Role of Framework Flexibility in Ion Transport: A Molecular Dynamics Study of LiM2IV(PO4)3

    Krishnanjan Pramanik, Kartik Sau, P. Padma Kumar

    The Journal of Physical Chemistry C　124　(7)　4001-4009　2020/01/23

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.jpcc.9b11624 　

    ISSN： 1932-7447

    eISSN： 1932-7455

  21. Role of divalent cation (Ba) substitution in the Li+ ion conductor LiTi2(PO4)3: a molecular dynamics study

    Kartik Sau, Tamio Ikeshoji, Supriya Roy

    Physical Chemistry Chemical Physics　22　(26)　14471-14479　2020

    Publisher: Royal Society of Chemistry (RSC)

    DOI： 10.1039/d0cp01053g 　

    ISSN： 1463-9076

    eISSN： 1463-9084

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    <p>Influence of Ba2+ ordering on cationic diffusion: (a) three-dimensional low Li+ ion diffusion using randomly substituted Ba2+, and (b) two-dimensional layered type high Li+ ion diffusion using specifically ordered substitution of Ba2+.</p>

  22. Reorientational motion and Li+ -ion transport in Li2B12H12 system: Molecular dynamics study

    Kartik Sau, Tamio Ikeshoji, Sangryun Kim, Shigeyuki Takagi, Kazuto Akagi, Shin-ichi Orimo

    Physical Review Materials　3　(7)　2019/07/15

    Publisher: American Physical Society (APS)

    DOI： 10.1103/physrevmaterials.3.075402 　

    eISSN： 2475-9953

  23. Influence of ion–ion correlation on Na+ transport in Na2Ni2TeO6: molecular dynamics study

    Kartik Sau

    Ionics　22　(12)　2379-2385　2016/07/27

    Publisher: Springer Science and Business Media LLC

    DOI： 10.1007/s11581-016-1782-2 　

    ISSN： 0947-7047

    eISSN： 1862-0760

  24. Ion-ion repulsion and entropic effects on Na+ transport in Na2Ni2TeO6: Molecular dynamics study

    Kartik Sau

    AIP Conference Proceedings　1728　020119-020119　2016

    Publisher: Author(s)

    DOI： 10.1063/1.4946170 　

    ISSN： 0094-243X

  25. Role of Ion–Ion Correlations on Fast Ion Transport: Molecular Dynamics Simulation of Na2Ni2TeO6

    Kartik Sau, P. Padma Kumar

    The Journal of Physical Chemistry C　119　(32)　18030-18037　2015/08/05

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/acs.jpcc.5b04087 　

    ISSN： 1932-7447

    eISSN： 1932-7455

  26. Ion Transport in Na2M2TeO6: Insights from Molecular Dynamics Simulation

    Kartik Sau, P. Padma Kumar

    The Journal of Physical Chemistry C　119　(4)　1651-1658　2015/01/20

    Publisher: American Chemical Society (ACS)

    DOI： 10.1021/jp5094349 　

    ISSN： 1932-7447

    eISSN： 1932-7455

  27. Molecular dynamics investigation of Na+ in Na2Ni2TeO6

    Kartik Sau, P. Padma Kumar

    AIP Conference Proceedings　2014/05

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Presentations 1

  1. Hydrogen-Metal Systems (Computational materials design for advanced hydrogen and solid-state battery materials)

    Kartik Sau

    Gordon Research Conference on Hydrogen-Metal Systems　2025/06