**Overview**

Research in the Zhu Group is centered around the mechanical properties and deformation mechanisms in a variety of material systems. We develop models and perform simulations using atomistic, continuum, and multiscale methods. The goal of our research is to design materials with significantly enhanced and potentially unprecedented performance. The recent research themes in the Zhu Group are outlined below.

**Ultra-strength Materials**

- Z. Li, Y. Zhang, Z. Zhang Y. Cui, Q. Guo, P. Liu, S. Jin, G. Sha, K. Ding, Z. Li, T. Fan, H. M. Urbassek, Q. Yu, T. Zhu, D. Zhang and Y. M. Wang. A nanodispersion-in-nanograins strategy for ultra-strong, ductile and stable metal nanocomposites.
*Nature Communications*, 13, 5581 (2022) - Z. Cheng, L. Bu, Y. Zhang, H. Wu, T. Zhu, H. Gao and L. Lu. Unraveling the origin of extra strengthening in gradient nanotwinned metals.
*Proceedings of the National Academy of Sciences of the USA*, 119, e2116808119 (2022) - R. Li, Q. Xie, Y. D. Wang, W. Liu, M. Wang, G. Wu, X. Li, M. Zhang, Z. P. Lu, C. Geng and T. Zhu. Unraveling submicron-scale mechanical heterogeneity by three-dimensional X-ray microdiffraction.
*Proceedings of the National Academy of Sciences of the USA*, 115, 483-488 (2018) - E. Ma and T. Zhu. Towards strength-ductility synergy through the design of heterogeneous nanostructures in metals.
*Materials Today*, 20, 323-331 (2017) - T. Zhu and J. Li. Ultra-strength materials.
*Progress in Materials Science*, 55, 710-757 (2010) - T. Zhu, J. Li, S. Ogata and S. Yip. Mechanics of ultra-strength materials.
*Materials Research Society Bulletin*, 34, 167-172, (2009) - T. Zhu, J. Li, A. Samanta, A. Leach and K. Gall. Temperature and strain-rate dependence of surface dislocation nucleation.
*Physical Review Letters*, 100, 025502 (2008) - T. Zhu, J. Li, A. Samanta, H. G. Kim and S. Suresh. Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals.
*Proceedings of the National Academy of Sciences of the USA*, 104, 3031-3036 (2007)

**In Situ Nanomechanics**

- L. Wang, Y. Zhang, Z. Zeng, H. Zhou, J. He, P. Liu, M. Chen, J. Han, D. J. Srolovitz, J. Teng, Y. Guo, G. Yang, D. Kong, E. Ma, Y. Hu, B. Yin, X. Huang, Z. Zhang, T. Zhu and X. Han. Tracking the sliding of grain boundaries at the atomic scale.
*Science*, 375, 1261–1265 (2022) - S. Chu, P. Liu, Y. Zhang, X. Wang, S. Song, T. Zhu, Z. Zhang, X. Han, B. Sun and M. Chen In situ atomic-scale observation of dislocation climb and grain boundary evolution in nanostructured metal.
*Nature Communications*, 13, 4151 (2022) - J. Wang, Z. Zeng, M. Wen, Q. Wang, D. Chen, Y. Zhang, P. Wang, H. Wang, Z. Zhang, S. X. Mao and T. Zhu. Anti-twinning in nanoscale tungsten.
*Science Advances*, 6, eaay2792 (2020) - Y. He, L. Zhong, F. Fan, C. Wang, T. Zhu and S. X. Mao. In situ observation of shear-driven amorphization in silicon crystals.
*Nature Nanotechnology*, 11, 866-871 (2016) - J. W. Wang, Z. Zeng, C. R. Weinberger, Z. Zhang, T. Zhu and S. X. Mao. In situ atomic-scale observation of twinning-dominated deformation in nanoscale body-centred cubic tungsten.
*Nature Materials*, 14, 594-600 (2015) - P. Zhang, L. Ma, F. Fan, Z. Zeng, C. Peng, P. E. Loya, Z. Liu, Y. Gong, J. Zhang, X. X. Zhang, P. M. Ajayan, T. Zhu and J. Lou. Fracture toughness of graphene.
*Nature Communications*, 5, 3782 (2014) - J. W. Wang, S. Narayanan, J. Y. Huang, Z. Zhang, T. Zhu and S. X. Mao. Atomic-scale dynamic process of deformation-induced stacking fault tetrahedra in gold nanocrystals.
*Nature Communications*, 4, 2340 (2013)

**3D-printed Materials**

- J. Ren, Y. Zhang, D. Zhao, Y. Chen, S. Guan, Y. Liu, L. Liu, S. Peng, F. Kong, J. D. Poplawsky, G. Gao, T. Voisin, K. An, Y. M. Wang, K. Y. Xie, T. Zhu and W. Chen. Strong yet ductile nanolamellar high-entropy alloys by additive manufacturing.
*Nature*, 608, 62–68 (2022) - Y. M. Wang, T. Voisin, J. T. McKeown, J. Ye, N. P. Calta, Z. Li, Z. Zeng, Y. Zhang, W. Chen, T. T. Roehling, R. T. Ott, M. K. Santala, P. J. Depond, M. J. Matthews, A. V. Hamza and T. Zhu. Additively manufactured hierarchical stainless steels with high strength and ductility.
*Nature Materials*, 17, 63-71 (2018) - W. Chen, T. Voisin, Y. Zhang, J. Florien, C. M. Spadaccini, D. L. McDowell, T. Zhu and Y. M. Wang. Microscale residual stresses in additively manufactured stainless steel.
*Nature Communications*, 10, 4338 (2019)

**High-entropy alloys**

- J. Ren, Y. Zhang, D. Zhao, Y. Chen, S. Guan, Y. Liu, L. Liu, S. Peng, F. Kong, J. D. Poplawsky, G. Gao, T. Voisin, K. An, Y. M. Wang, K. Y. Xie, T. Zhu and W. Chen. Strong yet ductile nanolamellar high-entropy alloys by additive manufacturing.
*Nature*, 608, 62–68 (2022) - H. Wang, D. Chen, X. An, Y. Zhang, S. Sun, Y. Tian, Z. Zhang, A. Wang, J. Liu, M. Song, S. P. Ringer, T. Zhu and X. Liao, Deformation-induced crystalline-to-amorphous phase transformation in a CrMnFeCoNi high-entropy alloy.
*Science Advances*, 7, eabe3105 (2021) - Q. Ding, Y. Zhang, X. Chen, X. Fu, D. Chen, S. Chen, L. Gu, F. Wei, H. Bei, Y. Gao, M. Wen, J. Li, Z. Zhang, T. Zhu, R. O. Ritchie and Q. Yu. Tuning element distribution, structure and properties by composition in high-entropy alloys.
*Nature*, 574, 223-227 (2019)

**Machine learning**

- Y. Zhang, Q. Li, T. Zhu and J. Li. Learning constitutive relations of plasticity using neural networks and full-field data.
*Extreme Mechanics Letters*, 52, 101645 (2022)

**Rechargeable Batteries**

- L. Zhang, T. Yang, C. Du, Q. Liu, Y. Tang, J. Zhao, B. Wang, T. Chen, Y. Sun, P. Jia, H. Li, L. Geng, J. Chen, H. Ye, Z. Wang, Y. Li, H. Sun, X. Li, Q. Dai, Y. Tang, Q. Peng, T. Shen, S. Zhang, T. Zhu and J. Huang. Lithium whisker growth and stress generation in an in situ atomic force microscope-environmental transmission electron microscope setup.
*Nature Nanotechnology*, 15, 94-98 (2020) - X. Wang, F. Fan, J. W. Wang, H. Wang, S. Tao, A. Yang, Y. Liu, H. B. Chew, S. X. Mao, T. Zhu, and S. Xia. High damage tolerance of electrochemically lithiated silicon.
*Nature Communications*, 6, 8417 (2015) - J. W. Wang, Y. He, F. Fan, X. H. Liu, S. Xia, Y. Liu, C. T. Harris, H. Li, J. Y. Huang, S. X. Mao and T. Zhu. Two-phase electrochemical lithiation in amorphous silicon.
*Nano Letters*, 13, 709-715 (2013) - S. Huang, F. Fan, J. Li, S. L. Zhang and T. Zhu. Stress generation during lithiation of high-capacity electrode particles in lithium ion batteries.
*Acta Materialia*, 61, 4354-4364 (2013) - X. H. Liu, J. W. Wang, S. Huang, F. Fan, X. Huang, Y. Liu, S. Krylyuk, J. Yoo, S. A. Dayeh, A. V. Davydov, S. X. Mao, S. T. Picraux, S. Zhang, J. Li, T. Zhu and J. Y. Huang. In situ atomic-scale imaging of electrochemical lithiation in silicon.
*Nature Nanotechnology*, 7, 749-756 (2012) - X. H. Liu, L. Zhong, S. Huang, S. X. Mao, T. Zhu and J. Y. Huang. Size dependent fracture of silicon nanoparticles during lithiation.
*ACS Nano*, 6, 1522-1531 (2012)

**2D Materials**

- Q. Zhu, Y. Hong, G. Cao, Y. Zhang, X. Zhang, K. Du, Z. Zhang, T. Zhu and J. Wang. Free-standing two-dimensional gold membranes produced by extreme mechanical thinning.
*ACS Nano*, 14, 17091-17099 (2020) - Y. Yang, X. Li, M. Wen, E. Hacopian, W. Chen, Y. Gong, J. Zhang, B. Li, W. Zhou, P. M. Ajayan, Q. Chen, T. Zhu and J. Lou. Brittle fracture of 2D MoSe2.
*Advanced Materials*, 29, 1604201 (2017) - P. Zhang, L. Ma, F. Fan, Z. Zeng, C. Peng, P. E. Loya, Z. Liu, Y. Gong, J. Zhang, X. X. Zhang, P. M. Ajayan, T. Zhu and J. Lou. Fracture toughness of graphene.
*Nature Communications*, 5, 3782 (2014)

**Shape Memory Alloys**

- Y. Zhong and T. Zhu. Phase field modeling of martensitic microstructure in NiTi shape memory alloys.
*Acta Materialia*, 75, 337-347 (2014) - Y. Zhong, K. Gall and T. Zhu. Atomistic characterization of pseudoelasticity and shape memory in NiTi nanopillars.
*Acta Materialia*, 60, 6301-6311 (2012)

**Multiscale Modeling**

- Y. Zhang, K. Ding, S. Stangebye, D. Chen, J. Kacher, O. Pierron and T. Zhu. Atomistic modeling of surface and grain boundary dislocation nucleation in FCC metals.
*Acta Materialia*, 237, 118155 (2022) - S. Narayanan, D. L. McDowell and T. Zhu. Crystal plasticity model for bcc iron atomistically informed by kinetics of correlated kinkpair nucleation on screw dislocation.
*Journal of the Mechanics and Physics of Solids*, 65, 54-68 (2014) - T. Zhu, J. Li and S. Yip. Atomistic reaction pathway sampling: the nudged elastic band method and nanomechanics applications.
*Nano and Cell Mechanics*(Eds. H. Espinosa and G. Bao), Chapter 12, John Wiley & Sons, 313-338 (2013) - T. Zhu, J. Li, A. Samanta, A. Leach and K. Gall. Temperature and strain-rate dependence of surface dislocation nucleation.
*Physical Review Letters*, 100, 025502 (2008) - T. Zhu, J. Li, A. Samanta, H. G. Kim and S. Suresh. Interfacial plasticity governs strain rate sensitivity and ductility in nanostructured metals.
*Proceedings of the National Academy of Sciences of the USA*, 104, 3031-3036 (2007) - T. Zhu, J. Li and S. Yip. Atomistic configurations and energetics of crack extension in silicon.
*Physical Review Letters*, 93, 205504 (2004) - T. Zhu, J. Li and S. Yip. Atomistic study of dislocation loop emission from a crack tip.
*Physical Review Letters*, 93, 025503 (2004)

**Research with undergraduate visitors**

The Zhu Group has hosted the visiting undergraduate students for research. Their representative publications are listed below.

- Xing Liu (Tsinghua University): A. K. Dickerson, X. Liu, T. Zhu and D. L. Hu. Fog spontaneously folds mosquito wings.
*Physics of Fluids*, 27, 021901 (2015) - Siyu Tao (Tsinghua University): X. Wang, F. Fan, J. W. Wang, H. Wang, S. Tao, A. Yang, Y. Liu, H. B. Chew, S. X. Mao, T. Zhu, and S. Xia. High damage tolerance of electrochemically lithiated silicon.
*Nature Communications*, 6, 8417 (2015) - Hao Zhou (Peking University): L. Wang, Y. Zhang, Z. Zeng, H. Zhou, J. He, P. Liu, M. Chen, J. Han, D. J. Srolovitz, J. Teng, Y. Guo, G. Yang, D. Kong, E. Ma, Y. Hu, B. Yin, X. Huang, Z. Zhang, T. Zhu and X. Han. Tracking the sliding of grain boundaries at the atomic scale.
*Science*, 375, 1261–1265 (2022) - Xiaohan Zhang (Tsinghua University): Q. Zhu, Y. Hong, G. Cao, Y. Zhang, X. Zhang, K. Du, Z. Zhang, T. Zhu and J. Wang. Free-standing two-dimensional gold membranes produced by extreme mechanical thinning.
*ACS Nano*, 14, 17091-17099 (2020) - Yongchao Chen (University of Science and Technology of China): Y. Lu, Y. Chen, Y. Zeng, Y. Zhang, D. Kong, X. Li, T. Zhu, X. Li, S. Mao, Z. Zhang, L. Wang and X. Han, Nanoscale ductile fracture and associated atomistic mechanisms in a body-centered cubic refractory metal.
*Nature Communications,*14, 5540 (2023)