Z Kristallogr 229:405–419Ītkinson AJ, Carpenter MA, Salje EKH (1999) Hard mode infrared spectroscopy of plagioclase feldspars. Phys Chem Miner 15:313–318Īngel RJ, Gonzales-Platas J, Alvaro M (2014) EosFit-7c and a Fortran module (library) for equation of state calculations. Contrib Mineral Petrol 146:506–512Īngel RJ, Hazen RM, McCormick TC, Prewitt CT, Smyth JR (1988) Comparative compressibility of end-member feldspars. This lack of interaction with the surrounding oxide lattice under compression may impact the stability of ammoniated minerals at high pressures and temperatures and ultimately likely favors nitrides or fluid phases as the dominant nitrogen carriers within the deeper mantle.Īngel RJ (2004) Equations of state of plagioclase feldspars. Hence, it appears that the ammonium ion interacts minimally with its surrounding lattice, even at high pressures: Its behavior is compatible with it being, aside from Coulombic attraction to the oxygen-dominated matrix, a largely non-interactive guest molecule within the silicate framework. These results show that (1) there is little, if any, enhancement of hydrogen bonding between the ammonium ion and the oxygen ions of the silica and aluminum tetrahedral framework under pressure, as manifested by the slight (and mostly positive) shifts in the N–H stretching vibrations of the ammonium ion (2) ordering of the ammonium ion is not observed under compression, as no changes in peak width or in the general appearance of the spectra are observed under compression and (3) structural changes induced by pressure in the aluminosilicate framework do not produce significant changes in the bonding of the ammonium ion. However, the vibrations of the aluminosilicate framework of buddingtonite undergo changes in their slope at ~13 GPa, implying that a change in compressional mechanism occurs near this pressure, but the vibrational modes of the ammonium molecule show little response to this change. Under compression, the N–H vibrations are remarkably insensitive to pressure throughout the pressure range of these experiments. Powder diffraction data yield a bulk modulus of 49 GPa for a pressure derivative of 4, implying that the ammonium ion substitution may induce a modest softening of the feldspar lattice relative to the potassium ion. We examine the bonding of the ammonium ion under pressure and in particular whether hydrogen bonding is enhanced by compaction, as well as probe how the ammonium ion affects the elasticity and behavior of the aluminosilicate framework at pressure. The equilibrium is reached when the number of molecules escaping from the liquid phase is the same as the number of molecules entering it.The behavior of the ammoniated feldspar buddingtonite, NH 4AlSi 3O 8, has been studied using infrared (IR) spectroscopy up to ~30 GPa and using synchrotron powder X-ray diffraction to 10 GPa at room temperature. See įor instance, this kind of "fight" also happens with evaporation inside a closed recipient. The speed of bonds breaking and the speed of recombination "fight" one another, until they are in chemical equilibrium, that is when both speeds are the same. Note that even though H+ and OH- are naturally produced in water, they also recombine back into H2O. By the way, that is what makes both pH and pOH of water equal 7. that is: covalent bonds are breaking all the time (self-ionization), just like intermolecular bonds (evaporation). The concentration of each of these ions in pure water, at 25☌, and pressure of 1atm, is 1.0×10e−7mol/L. But, then, why no hydrogen or oxygen is observed as a product of pure water? Because water decomposes into H+ and OH- when the covalent bond breaks. Water, for example is always evaporating, even if not boiling. Yes, they can both break at the same time, it is just a matter of probability.
Statistically, intermolecular bonds will break more often than covalent or ionic bonds. Intermolecular bonds break easier, but that does not mean first.
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