A first-principles study of the structural and elastic properties of orthorhombic and tetragonal Ca3Mn2O7 |
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| Affiliation: | [1]Department of Physics, Institute of Theoretical Physics, Nanjing Normal University, Nanjing 210023, China [2]Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems, Nanjing Normal University, Nanjing 210023, China |
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| Abstract: | ![]()
The structural and elastic properties of multiferroic Ca3Mn2O7 with ferroelectric orthorhombic(O-phase) and paraelectric tetragonal structures(T-phase) have been studied by first-principles calculations within the generalized gradient approximation(GGA) and the GGA plus Hubbard U approaches(GGA+U).The calculated theoretical structures are in good agreement with the experimental values.The T-phase is found to be antiferromagnetic(AFM) and the AFM O-phase is more stable than the T-phase,which also agree with the experiments.On these bases,the single-crystal elastic constants(Cij s) and elastic properties of polycrystalline aggregates are investigated for the two phases.Our elasticity calculations indicate Ca3Mn2O7 is mechanically stable against volume expansions.The AFM O-phase is found to be a ductile material,while the AFM T-phase shows brittle nature and tends to be elastically isotropic.We also investigate the influence of strong correlation effects on the elastic properties,qualitatively consistent results are obtained in a reasonable range of values of U.Finally,the ionicity is discussed by Bader analysis.Our work provides useful guidance for the experimental elasticity measurements of Ca3Mn2O7,and makes the strain energy calculation in multiferroic Ca3Mn2O7 thin films possible. |
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| Keywords: | elastic constant elastic anisotropy strong correlation effect multiferroic |
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