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Fibrous phosphorus is one of the known crystalline allotropes under standard pressure conditions. It has been predicted prior to its successful synthesis and structural characterization. The allotrope consists of parallel, tubular double strands of phosphorus, in contrast to the violet form of Hittorf's phosphorus, where the same strands are arranged in a perpendicular orientation towards each other. This structural similarity results in an almost identical energetic stability leading to a somehow problematic realization of single-phase materials. We herein report on the successful synthesis route to single phase fibrous phosphorus and the in situ characterization of its formation via the gas phase applying CuCl2 as a mineralizer. The sublimation pressure of fibrous phosphorus is slightly lower than the one of the black allotrope. This behavior indicates thermodynamic stability of fibrous phosphorus.
Phase pure polycrystalline PbP7 was prepared from the elements via a lead flux. Crystalline pieces with edge-lengths up to 1 mm were obtained. The assignment of the previously published 31P solid state NMR spectrum to the seven distinct crystallographic sites was accomplished by radio-frequency driven dipolar recoupling (RFDR) experiments. As commonly found in other solid polyphosphides there is no obvious correlation between the 31P chemical shift and structural parameters. PbP7 decomposes incongruently under release of phosphorus forming liquid lead as remainder. The thermal decomposition starts at T>550 K with a vapor pressure almost similar to that of red phosphorus. Electronic structure calculations reveal PbP7 as a semiconductor according to the Zintl description and clearly shows the stereo-active Pb-6s2 lone pairs in the electron localization function ELF.
SnIP is the first atomic-scale double helical semiconductor featuring a 1.86 eV bandgap, high structural and mechanical flexibility, and reasonable thermal stability up to 600 K. It is accessible on a gram scale and consists of a racemic mixture of right- and left-handed double helices composed by [SnI] and [P] helices. SnIP nanorods <20 nm in diameter can be accessed mechanically and chemically within minutes.
The application of the EnPhaSyn (theoretical Energy diagrams, experimental Phase formation, Synthesis and characterisation) concept is reviewed with respect to prediction of structures and stability of element allotropes and compound polymorphs, their phase formation and transition processes, and their directed synthesis, respectively. Therein, the relative energetical stability (En) of target compounds and possible decomposition are determined from quantum chemical DFT calculations. Phase formation and transition (Pha) is probed by a gas balance method, developed as high temperature gas balance concept. It helped to study the synthesis and stability range of several compounds experimentally. Applications of the concept and synthesis principles (Syn) of non-equilibrium phases are presented for allotropes of P, As, P1-xAsx, as well as binary and ternary compounds including the Zintl and Laves like phases IrPTe, NiP2, CoSbS, NiBiSe, Li0.2CdP2, Cu3CdCuP10, and Cd4Cu7As.
Calculation of electromotive series of solids allows easy prediction of reaction pathways[1]. Using the electromotive series of systems As-P-O and As-P-X (X = F, Cl, Br, I) the formation of element allotropes via the oxide and halide compounds in thermite type reactions can be deduced: phosphorous will reduce the arsenic oxides to elemental arsenic, forming grey or black allotrope, depending on reaction mixture composition.