Mechanical properties of siderite and hematite from DFT calculation

•Elastic constant matrixes of siderite and hematite have been calculated.•For siderite and hematite, shear deformation pattern is easiest to take place.•Young’s modulus, Poisson’s ratio, B/G, and compressibility were calculated.•Young’s modulus distribution on crystal surfaces was plotted.•Smaller minimum Young’s modulus of siderite caused the easy sliming of siderite. Aiming to reveal the easy-sliming mechanism of siderite in the grinding process of carbonate-bearing iron ores, mechanical properties of siderite and hematite were computed by density functional theory (DFT). Elastic constant matrixes were developed and results show that shear deformation is the easiest deformation type compared to other types for both siderite and hematite crystal. Based on the elastic constant matrixes, bulk modulus and shear modulus of siderite and hematite were calculated and their ratios of bulk modulus to shear modulus (B/G) are 2.17 and 2.61 respectively, which suggested that siderite fractured more easily than hematite under the same stress level. Consequently, Young’s modulus, Poisson’s ratio, and compressibility were also calculated. Elastic anisotropy was investigated by computing the distribution of Young’s modulus with crystallographic direction. The color contour surfaces demonstrated that siderite crystal was strongly anisotropic in comparison with hematite, and the minimum Young’s modulus of siderite was only the half of that of hematite, which indicates the underlying mechanism that siderite slimed easily when milled with hematite. In addition, this study provides a novel understanding concerning how mechanical properties of mineral crystals affect grinding processes, paving the way for selective grinding to avoid the easy-sliming of certain minerals.