Discovery of gamma -MnP sub(4) and the Polymorphism of Manganese Tetraphosphide

A new polymorph of MnP sub(4) was prepared by reaction of the elements via chemical vapor transport with iodine as transporting agent. The crystal structure was refined using single-crystal diffraction data (space group Cc, no. 9, a = 5.1049(8) [Angstrom], b = 10.540(2) [Angstrom], c = 10.875(2) [An...

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Bibliographic Details
Published in:Inorganic chemistry 2015-09, Vol.54 (17), p.8761-8768
Main Authors: Henge, Dennis B, Hermus, Martin, Litterscheid, Christian F, Wagner, Norbert, Beck, Johannes, Albert, Barbara, Brgoch, Jakoah
Format: Article
Language:English
Subjects:
Anisotropy
Diffraction
Electronics
Manganese
Mathematical analysis
Phonons
Resistivity
Stacking
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Summary:A new polymorph of MnP sub(4) was prepared by reaction of the elements via chemical vapor transport with iodine as transporting agent. The crystal structure was refined using single-crystal diffraction data (space group Cc, no. 9, a = 5.1049(8) [Angstrom], b = 10.540(2) [Angstrom], c = 10.875(2) [Angstrom], beta = 93.80(2)[degrees]). The phase is called gamma -MnP sub(4) as it is isostructural with gamma -FeP sub(4). It is the fourth reported binary polymorph in the MnP sub(4) system, all of which are stacking variants of nets built with manganese and phosphorus atoms. In gamma -MnP sub(4), there are two Mn-Mn distances (2.93 and 3.72 [Angstrom]) arising from a Peierls-like distortion effectively forming Mn sub(2) dumbbells in the structure. Magnetic and electrical conductivity measurements show diamagnetism and a small anisotropic band gap (100-200 meV) with significantly enhanced conductivity along the crystallographic a axis. Calculations of the electronic and vibrational (phonon) structures show the P-P and Mn-P bonds within the nets are mainly responsible for the stability of the phase. The similar bonding motifs of the polymorphs give rise to the existence of numerous dynamically stable variants. The calculated Helmholtz energy shows the polymorph formation to be closely tied to temperature with the 6-MnP sub(4) structure favorable at low temperatures, the 2-MnP sub(4) favorable between approximately 800 and 2000 K, and 8-MnP sub(4) preferred at high temperatures.
ISSN:0020-1669
DOI:10.1021/acs.inorgchem.5b01372