The Couplings of Rock/Carbonate Groundwater/Cement Leachate

Hyper-alkaline cement leachates generated from the cement buffer of a nuclear waste disposal site have significant influences on the mineralogy of the host rock, creating a chemically disturbed zone (CDZ). Three major types of cement leachates are formed during the evolution process. Most of the existing scenario modelling research has been focused on the influence of the cement leachate on the host rock. However, the influence of the groundwater in the host rock on the evolution of the CDZ remains unexplored. This paper presents a numerical scenario modelling of the couplings among carbonate groundwater, cement leachates and rock minerals. The results reveal that the high carbonate groundwater significantly affects the precipitation of calcium silicate hydrate (C-S-H) and calcite, and consequently alters the physical and chemical properties of the host rock. This finding provides an essential guide for selection of the location of geological disposal facility (GDF) in terms of the groundwater chemistry

Quasiclassical trajectory study of the SiH4+H→SiH3+H2 reaction on a global ab initio potential energy surface

The SiH4+H→SiH3+H2 reaction has been investigated by the quasiclassical trajectory (QCT) method on a recent global ab initio potential energy surface [ M. Wang et al., J. Chem. Phys. 124, 234311 (2006) ]. The integral cross section as a function of collision energy and thermal rate coefficient for the temperature range of 300–1600 K have been obtained. At the collision energy of 9.41 kcal/mol, product energy distributions and rovibrational populations are explored in detail, and H2 rotational state distributions show a clear evidence of two reaction mechanisms. One is the conventional rebound mechanism and the other is the stripping mechanism similar to what has recently been found in the reaction of CD4+H [ J. P. Camden et al., J. Am. Chem. Soc. 127, 11898 (2005) ]. The computed rate coefficients with the zero-point energy correction are in good agreement with the available experimental data