Sphalerite lattice energy

This topic will be discussed in two steps, firstly the crystals with 3-dimensional structures (metal nanoparticles and 4-coordinate semiconductors) and then those with a layered stmcture (Bi, Se, Te, etc). A decrease in the crystal sizes can result in a change of the stmcture type if the surface energy gain exceeds the enthalpy of the corresponding phase transition. Thus, Co has the structure of the hep type in the bulk, the/cc type in 10-20 nm particles and the bcc type in 2-5 nm particles [33], Particles of In with the diameter of <5 nm have the/cc structure, and those from 5 nm upward to the bulk have the fecf-lattice [34]. Agl adopts the cubic stmcture in the particles larger than 50 nm and the hexagonal one in smaller crystals [35]. In As has the wurtzite (w) stmcture up to 40 nm and the sphalerite (zb) structure in grains of >80 nm [36]. Nano-CdS has the the zb stmcture for D = 4 nm, while the w-phase is stable for the bulk material [37, 38]. On the contrary, MnSe was obtained in the w-form in nanoparticles, whereas the zb phase is stable for bulk crystals [37, 39]. 

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