Search results for "Chemical thermodynamic"
showing 5 items of 5 documents
Towards highly accurate ab initio thermochemistry of larger systems: benzene.
2011
The high accuracy extrapolated ab initio thermochemistry (HEAT) protocol is applied to compute the total atomization energy (TAE) and the heat of formation of benzene. Large-scale coupled-cluster calculations with more than 1500 basis functions and 42 correlated electrons as well as zero-point energies based on full cubic and (semi)diagonal quartic force fields obtained with the coupled-cluster singles and doubles with perturbative treatment of the triples method and atomic natural orbital (ANO) triple- and quadruple-zeta basis sets are presented. The performance of modifications to the HEAT scheme and the scaling properties of its contributions with respect to the system size are investiga…
Degassing vs. eruptive styles at Mt. Etna volcano (Sicily, Italy). Part I: Volatile stocking, gas fluxing, and the shift from low-energy to highly ex…
2018
International audience; Basaltic magmas can transport and release large amounts of volatiles into the atmosphere, especially in subduction zones, where slab-derived fluids enrich the mantle wedge. Depending on magma volatile content, basaltic volcanoes thus display a wide spectrum of eruptive styles, from common Strombolian-type activity to Plinian events. Mt. Etna, in Sicily, is a typical basaltic volcano where the volatile control on such a variable activity can be investigated. Based on a melt inclusion study in products from Strombolian or lava-fountain activity to Plinian eruptions, here we show that for the same initial volatile content, different eruptive styles reflect variable dega…
Chemical heterogeneities in the mantle: The equilibrium thermodynamic approach
2016
Abstract This study attempts to answer a simple and yet fundamental question in relation to our understanding of the chemical evolution of deep Earth and planetary interiors. Given two initially separate assemblages (lithologies) in chemical equilibrium can we predict the chemical and mineralogical compositions of the two assemblages when they are put together to form a new equilibrated system? Perhaps a common perception is that given sufficient time, the two assemblages will homogenize chemically and mineralogically, however from a chemical thermodynamic point of view, this is not the case. Certain petrological differences in terms of bulk composition, mineralogy and mineral abundance rem…
High-accuracy extrapolated ab initio thermochemistry. III. Additional improvements and overview
2008
Effects of increased basis-set size as well as a correlated treatment of the diagonal Born-Oppenheimer approximation are studied within the context of the high-accuracy extrapolated ab initio thermochemistry (HEAT) theoretical model chemistry. It is found that the addition of these ostensible improvements does little to increase the overall accuracy of HEAT for the determination of molecular atomization energies. Fortuitous cancellation of high-level effects is shown to give the overall HEAT strategy an accuracy that is, in fact, higher than most of its individual components. In addition, the issue of core-valence electron correlation separation is explored; it is found that approximate add…
A novel thermodynamic approach for the complexation study of toxic metal cations by a landfill leachate
2018
Landfill leachates can contaminate nearby aquifers. The hazards deriving from this contamination also depend on the chemical speciation of various contaminants. A novel approach is proposed here to face this problem from a chemical thermodynamics point of view. The complexing ability of the soluble fraction of a landfill leachate (collected from Bellolampo, Palermo, Italy) towards Pb2+, Cd2+ and Cu2+ has been investigated at T = 298.15 K in NaClaq at I = 0.1 mol dm−3. The soluble fraction of the landfill leachate was first characterized by different analytical techniques. Then, its acid–base properties were studied by ISE-H+ potentiometric titrations and modelled by the so-called diprotic-l…