The effects of temperature and indentation parameters on mechanical properties of calcite through molecular dynamics simulation

Abstract

The extraction of deep energy resources often encounters high-temperature environments, making it challenging to drill cores and conduct conventional rock mechanics tests to explore the mechanical properties of reservoir rocks. Currently, the methods to study the effects of temperature on rock minerals are quite limited. Based on molecular dynamics and considering the effect of temperature on rock minerals properties, the analysis and simulation method for rock mechanical properties in indentation tests are proposed. This paper elucidates the influence of temperature on the mechanical behavior of calcite from three aspects: nanoindentation results, atomic displacement, and strain. Simulation results show that the differences between the load–displacement curves of distinct crystal planes decrease as temperature increases, suggesting that temperature weakens the anisotropy of calcite to a certain extent. The indentation modulus initially increases and then decreases as the temperature increases, and the elastic recovery rate calculated based on the indentation morphology also shows this trend, elucidating the relationship between the weakening effect of high temperature and the constraining effect of the specimen. Increasing the temperature not only increases the displacement of calcite but also strengthens plastic deformation. The direction and extent of internal deformation propagation at different crystal planes show variations with increasing temperature, and the indentation accumulation gradually presents an asymmetric distribution. Additionally, we investigated the nanoindentation process of calcite under different indentation parameters, revealing that changes in indentation depth and the indenter radius can reflect the different elastic responses of crystal planes. Higher loading velocities enhance the strength of calcite and induce less plastic deformation. This work contributes to a deeper understanding of the microscopic deformation mechanisms of deep rocks and provides theoretical guidance for conducting nanoindentation tests on deep rocks.