Manganese oxides with layer and tunnel structures occur widely in the natural environment and inspire technological applications. In addition to having variable compositions, these structures often are found as small particles (nanophases). This study explores, using experimental thermochemistry, the role of composition, oxidation state, structure, and surface energy in the thermodynamic stability of synthetic birnessites and cryptomelane. These quantitative thermodynamic findings help explain

more »

... nd support qualitative observations of phase-transformation patterns gathered over the past five decades. (See pp. E1046-E1053.