Effect of Surface Energetics on Phase Stability of CaMnO₃

Abstract

CaMnO3 is a promising starting point for the search of perovskites which are suitable as electrode materials for the hydrogen evolution reaction (HER). In a previous theoretical study [Phys. Status Solidi B 2022, 260, 2200427], it was established that the global hybrid functional PW1PW is well suited to obtain structural, energetic, and electronic bulk properties. Herein, the focus is extended to surface properties of CaMnO3. All symmetry‐inequivalent low‐index surfaces of CaMnO3 are investigated with PW1PW. Based on the experience with polar surfaces, it is decided to employ stoichiometric and symmetric models, in some cases with Schottky defects. From the calculated surface energies, the crystal morphologies are predicted based on the Gibbs–Wulff theorem. The (101), (100), (011), (001), and (010) surfaces (space group no. 62) and the (010), (110), (011), and (101) surfaces (space group no. 20) dominate the surfaces of respective single crystals and should be considered in future theoretical calculations of the HER. Furthermore, it is found that the modification with space group no. 20 is significantly more stable than space group no. 62 for nanoparticles with a diameter below 10 nm.

Defect Formation Thermodynamics of (A,A′)(B,B′)O3 (A = Mg,Ca,Sr and B = Ti,Mn,Cr,Fe,Mo) Perovskites

“…The average OVF energy of the first two defects () for (here SG 20) is 180.3 kJ mol −1 , which is 27 kJ mol −1 larger than that was determined previously for in SG 62. [ 12 ] The difference is related to the different structures of the two space groups. It can also be due to the less intensive search for the most stable OV configuration for .…”

“…The global hybrid functional PW1PW [ 9 ] was used in combination with the pob‐TZVP‐rev2 solid‐state basis sets, [ 10,11 ] since this provided the most accurate results for the defect formation thermodynamics of . [ 12 ] The Monkhorst–Pack grid was adapted to each crystal structure to ensure sufficiently high k ‐point density. The integration truncation parameters TOLINTEG were set to 7,7,7,7,14.…”

“…Vibrational contributions to the thermodynamic functions were neglected here because we found in recent work that the frequencies are not very sensitive to small structural changes. [ 12 ]…”

Ultrasensitive Electrochemiluminescence Biosensor Based on Efficient Signal Amplification of Copper Nanoclusters Induced by CaMnO3 for CD44 Trace Detection

“…Sensitivity is an important criterion for measuring the detection ability of sensors, while a strong output signal is a prerequisite for improving sensitivity. , On this basis, CaMnO 3 was introduced as a co-reaction promoter for catalyzing co-reactants to generate more reactive radicals, thereby enhancing the ECL responses of Cu NCs. More specifically, CaMnO 3 had a redox pair of Mn 3+ /Mn 4+ , which could better promote the reduction of persulfate, thus generating more sulfate radicals (SO 4 •– ) to improve the ECL emissions of Cu NCs. , Meanwhile, it also had a large specific surface area, which provided a larger contact area with co-reactants, thus further enhancing the catalytic activity. − To further improve the detection sensitivity of biosensors, we introduced an antibody affinity ligand to improve the binding ability of the antibodies. The Fc fragments of antibodies could be specifically bound by the introduction of the peptide ligand (NARKFYKGC, NAR), thus releasing more antigen-binding regions to enhance the antigen–antibody binding efficiency, which ultimately achieved the goal of increasing sensitivity. ,− …”

Theoretical Study on Proton Migration on the CaMnO3 Surface

“…In this work, the migration of proton from the CaMnO 3 surface into the bulk will be investigated in more detail. The (100) and (010) surfaces of the experimentally found orthorhombic polymorph (space group 62) are considered, which together account for about 50% of the total surface area of CaMnO 3 single crystals . First, the oxygen defect formation energies and hydration energies are computed for the first four layers of both surfaces for CaMnO 3 and CaMn 0.75 Fe 0.25 O 3 .…”