Abstract
Synchrotron Radiation X-ray Photoelectron Spectroscopy (SRXPS) and conventional X-ray Photoelectron Spectroscopy (XPS) of pristine (unreacted) loellingite fracture surfaces reveal two distinct contributions to the As 3d spectrum. One is derived from As atoms of the bulk phase (fully coordinated As atoms) and the other is derived from polymeric As species located on fracture surfaces. Surface polymerization reactions probably proceed in response to fracture whereby As dimers at the surface react to produce surface tetramers and possibly surface heptamers. Trimeric and pentameric species may form where As-As bond scission occurs during fracture.
The (001) surface of loellingite is autocompensated and unlikely to undergo reconstruction. The (010) and (100) surfaces are, however, arsenic-terminated and uncompensated, and surface reconstruction is expected. The short “c” dimension of the loellingite unit cell is critically important to surface polymerization because arsenic dimers on (100) and (010) surfaces are separated by 2.88 Å (normal to c) which is only 16% greater than the As-As bond length. Because of the short distance, adjacent surface dimers likely tilt toward each other and bond to produce surface tetramers. This should introduce minimal strain and eliminate high-energy dangling bonds thus stabilizing the surface. The polymerization reaction also explains the absence of surface (core-level-shifted) As dimeric and monomeric signals such as observed on pyrite surfaces
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Thermal equations of state for B1 and B2 KCl
- Determination of molar absorptivities for infrared absorption bands of H2O in andesitic glasses
- H2O activity in H2O-N2 fluids at high pressure and temperature measured by the brucitepericlase equilibrium
- Kinetics of iron oxidation-reduction in hydrous silicic melts
- Kinetics of cation ordering in synthetic MgAl2O4 spinel
- Structural properties and heat-induced oxidation-dehydrogenation of manganoan ilvaite from Perda Niedda mine, Sardinia, Italy
- Ultrahigh-pressure metamorphism in western Tianshan, China: Part I. Evidence from inclusions of coesite pseudomorphs in garnet and from quartz exsolution lamellae in omphacite in eclogites
- Ultra-high pressure metamorphism in western Tianshan, China: Part II. Evidence from magnesite in eclogite
- Discovery of clinoenstatite in garnet pyroxenites from the Dabie-Sulu ultrahigh-pressure terrane, east-central China
- Ultrahigh-pressure (UHP) low-Al titanites from carbonate-bearing rocks in Dabieshan- Sulu UHP terrane, eastern China
- Metamictization and recrystallization of titanite: An infrared spectroscopic study
- Fine structure of infrared OH-stretching bands in natural and heat-treated amphiboles of the tremolite-ferro-actinolite series
- Correlation between OH concentration and oxygen isotope diffusion rate in diopsides from the Adirondack Mountains, New York
- The substitution Fe3+-Al and the isosymmetric displacive phase transition in synthetic zoisite: A powder X-ray and infrared spectroscopy study
- In situ X-ray observation of the reaction dolomite = aragonite + magnesite at 900–1300 K
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- Synthesis and NMR characterization (1H and 31P MAS) of the fluorine-free hydroxylapatite–britholite-(Y) series
- Quantum mechanical calculations of dioctahedral 2:1 phyllosilicates: Effect of octahedral cation distributions in pyrophyllite, illite, and smectite
- The nature of disorder in montmorillonite by simulation of X-ray powder patterns
- Ferripedrizite, a new monoclinic BLi amphibole end-member from the Eastern Pedriza Massif, Sierra de Guadarrama, Spain, and a restatement of the nomenclature of Mg-Fe-Mn-Li amphiboles
- Description and crystal structure of vajdakite, [(Mo6+O2)2(H2O)2 As3+ 2O5]·H2O—A new mineral from Jáchymov, Czech Republic
- Some remarks on fission-track observational biases and crystallographic orientation effects
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- The strength of moissanite
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- Anisotropic Fe-Mg diffusion in biotite
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