Quenched Solid Density Functional Theory

Neimark AV, Lin Y, Ravikovitch PI, Thommes M Quenched solid density functional theory and pore size analysis of micro-mesoporous carbons. Carbon 47(7) 1617-1628, 2009. 

QSDFT Quenched solid density functional theory... 

FIGURE 13.7 Normalized pore size distributions (Nj-sorption, deconvolution via QSDFT quenched solid density functional theory) for SiC powder with parallel and subsequent COj activation and Clj extraction. 

Figure 8.6 Nitrogen adsorption/desorption AC-PVDF electrodes. For the electrodes, the isotherms obtained at 77 K (a) and quenched amount of nitrogen adsorbed is referred to solid density functional theory (QSDFT) pore the mass of AC [60]. size distribution (b) of AC, AC-PTFE, and...

We suggest a model of adsorption in pores with amorphous and microporous solid walls, named the quenched solid non-local density functional theory (QSNLDFT) model. We consider a multicomponent non-local density functional theory (NLDFT), in which the solid is treated as a quenched component with a fixed spatially distributed density. Drawing on several prominent examples, we show that QSNLDFT model produces smooth Isotherms of mono- and polymolecular adsorption, which resemble experimental isotherms on amorphous surfaces. The model reproduces typical behaviors of N2 isotherms on micro- mesoporous materials, such as SBA-15. QSNLDFT model offers a systematic approach to the account for the surface roughness/heterogeneity in pore structure characterization methods. 

In this paper, we suggest a systematic approach that extends the applicability of NLDFT models to heterogeneous surfaces of amorphous and microporous solids. The main idea is to use a multicomponent NLDFT, in which the solid is treated as one of the components with a fixed spatially distributed density. The model, named quenched solid non-local density functional theory (QSNLDFT), is an extension of the quenehed-annealed DFT model of systems with hard-core interactions recently proposed by Schmidt and coworkers [23,24]. Drawing on several prominent examples, we show that the proposed model produces smooth isotherms in the region of multiplayer adsorption. Moreover, the effects of wall microporosity can be naturally incorporated into the model. Although the parameters of the model have not been yet optimized to describe quantitatively a particular experimental system, the model generates adsorption isotherms which are in qualitative agreement with experimental isotherms of N2 or Ar adsorption on amorphous silica materials. 

The model (2)-(4) is referred to as the quenched solid non-local density functional theory (QSNLDFT). There are several advantages in considering the solid as a quenched component of the system rather than a source of the external field. On the one hand, this approach offers flexibility in the description of the fluid-solid boundary by varying the solid density and the thickness of the diffuse solid surface layer. On the other hand, it retains the main advantage of NLDFT computational efficiency because even a one-dimensional solid density distribution ceui include the effects of surface roughness and heterogeneity. For example, the solid density distribution can be taken from simulations of amorphous silica surfaces [29,30]. 

We start with the question of what happens to the large orbital moment of f electrons when they are hybridized with other states in solids. This question, of course, is central to understanding the unusual properties of actinide (and cerium) compounds. Form-factor measurements had shown the importance of hybridization effects in compounds such as UGej (Lander et al. 1980), but at that time no theory had been developed to handle these effects in particular the orbital contribution was known to be incorrectly treated in band-structure calculations (Brooks et al. 1984, Brooks 1985). Brooks, Johansson, and their collaborators corrected this deficiency by adding an orbital polarization term in the density-functional approximation (see the chapter by Brooks and Johansson (ch. 112) in this volume). When they made calculations on a series of intermetallic compounds, particularly those with a transition metal in the compact fee Laves phase, they found that the value of was reduced compared to the free-ion values. Loosely speaking, we can associate such a partial quenching of the /j ,-value with the fact that the 5f electrons have become partially itinerant, and we know that fully itinerant electrons (in the 3d metals, for example) have 0. 

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