**4. Conclusions**

Molecular dynamic simulations were conducted to investigate the mechanical properties of montmorillonite with different compensation cations upon hydration with unconstrained system atoms, expanding further studies of nanoscale elastic properties. The conclusions are as follows:


The simulation results reveal that the water molecules linked to the mineral surface will be arranged in an ordered structure (H-bond formation and thermodynamic dense stable state) and their shear strength are not zero. Preliminary discussion shows that this is related to the strength mechanism of clay at the microscale. Building a bottom-up procedure toward a constitutive law for soil mechanical still needs further research.

**Author Contributions:** Conceptualization, L.K. and Q.Z.; Methodology, X.S.; Validation, X.Z.; Formal analysis, L.K.; investigation, Q.Z.; writing—original draft preparation, L.K Writing-Original Draft Preparation, L.K.; Writing—review and editing, Q.Z. and X.Z.; Visualization, X.S.; Supervision, Q.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Fundamental Research Funds for the Central Universities, grant number 2020ZDPYMS18.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** The study presented in this article was supported by the Fundamental Research Funds for the Central Universities (2020ZDPYMS18). This support is gratefully acknowledged.

**Conflicts of Interest:** The authors declare no conflict of interest.
