Insights into the structural, thermodynamic, electronic, and mechanical properties of CaMn2O4 polymorphs via density functional theory analysis

Abstract The search for alternative energy storage battery chemistries has become increasingly important in recent years due to the projected lithium depletion and high costs of Li-ion batteries. As an alternative to Li-ion, research on the bivalent Ca-ion has gained momentum in developing new rechargeable battery chemistries. This work conducted ab initio computational simulations to investigate the structural, thermodynamic, electronic, and mechanical behaviour of the Fd3m-CaMn 2 O 4 , Pbcm-CaMn 2 O 4 , and Imma-CaMn 2 O 4 polymorphs. The structural lattice parameters computed for Pbcm-CaMn 2 O 4 exhibited favourable agreement with experimental data; the percentage difference between the experimental and simulated parameters is less than 6%, confirming the validity of the methodology used. The negative enthalpies of formation indicated that the three CaMn 2 O 4 polymorphs being studied are thermodynamically stable and can be readily synthesized experimentally. Moreover, the phonon dispersion curves predicted dynamical stability on the Pbcm-CaMn 2 O 4 , and Imma-CaMn 2 O 4 polymorphs, while the Fd3m-CaMn 2 O 4 depicted negative frequencies along high-symmetry directions of the Brillouin zone. Analysis of the densities of states revealed that all three polymorphs can be classified as conductors. Lastly, the values of elastic constants indicated that Fd3m-CaMn 2 O 4 , Pbcm-CaMn 2 O 4 and Imma-CaMn 2 O 4 are elastically stable, while the strain–stress relationship showed a relatively large elastic limit.