Fighting coal — Effectiveness of coal-replacement programs for residential heating in China: Empirical findings from a household survey

Household fuel substitution has been a crucial step for controlling air pollution in China, but the performance evaluation of household fuel substitution policies is overlooked. This study capitalized on the opportunity to use data collected during the household coal-replacement program in North China to evaluate the effect of a mandatory policy on fuel substitution at the micro-level. The results indicate that there is a significant effect of the coal-replacement program on fuel substitution, as we expected. The coal-to-electricity policy is effective in achieving the goal of a clean winter but not a warm winter due to the decline of delivered energy, while the high-quality coal replacement policy results in better performance in delivered energy but no improvement in indoor air quality. It is recommended to prioritize supporting measures on both the supply and demand sides before implementation, along with undertaking differential measures during the implementation phase to better address energy inequality

Stable T2Sin (T=Fe,Co,Ni,1≤n≤8) cluster motifs

First principles studies on the geometry, electronic structure, and magnetic properties of neutral and anionic Fe2Sin, Co2Sin, and Ni2Sin (1≤n≤8) clusters have been carried out within a gradient corrected density functional framework. It is shown that these clusters display a variety of magnetic species with varying magnetic moment and different magnetic coupling between the two transition metal atoms. While Fe2Sin clusters are mostly ferromagnetic with large moments, Ni2Sin clusters are mostly nonmagnetic. Our studies of the variation of the binding energy upon addition of successive Si atoms and the gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital indicate that many of the motifs are quite stable and could be suitable as building blocks for generating magnetic cluster assembled materials. The studies also reveal motifs that could be used in molecular electronic devices to generate spin polarized currents or large magnetoresistance

The effect of substituted benzene dicarboxylic acid linkers on the optical band gap energy and magnetic coupling in manganese trimer metal organic frameworks

We have systematically studied a series of eight metal-organic frameworks (MOFs) in which the secondary building unit is a manganese trimer cluster, and the linkers are differently substituted benzene dicarboxylic acids (BDC). The optical band gap energy of the compounds vary from 2.62 eV to 3.57 eV, and theoretical studies find that different functional groups result in new states in the conduction band, which lie in the gap and lower the optical band gap energy. The optical absorption between the filled Mn 3d states and the ligands is weak due to minimal overlap of the states, and the measured optical band gap energy is due to transitions on the BDC linker. The Mn atoms in the MOFs have local moments of 5 mu B, and selected MOFs are found to be antiferromagnetic, with weak coupling between the cluster units, and paramagnetic above 10 K

Quantum size effect on the magnetism of finite systems

Journal ArticleThe magnetic moments of the ferromagnetic transition metals Fe, Co, and Ni confined to one-dimensional chains are found to fluctuate with increasing chain length before converging to the infinite limit. This quantum size effect is derived from a simple first-principles theory that we have developed to study the evolution of the electronic structure of systems as a function of size and dimensionality. The quantitative accuracy of the predictions of this simple formulation is confirmed by carrying out ab initio self-consistent calculations using the molecular-orbital approach. The convergence of moments to the respective infinite limit is found to depend on the dimensionality of the system

Effect of size and dimensionality on the magnetic moment of transition metals

Journal ArticleThe effect of size and dimensionality on the magnetic moments of Fe, Co, and Ni have been studied theoretically by confining the atoms t o various structural forms such as chains,surfaces, and thin films. The size of these systems is controlled by limiting t h e number of atoms. A new first-principles theory is developed that enables us to study the electron spin density of states and moments of atoms in clusters containing two to a few thousand atoms. The theory is based upon t h e elementary principles governing t h e tight binding and linear combination of atomic orbitals formulations. It contains no adjustable parameters and can be applied to systems with or without topological symmetry. We have discovered quantum size effects on t h e magnetic moments of linear chains and these effects disappear when the chains contain more than 20 atoms. We have also found distinct effects of the local environment on the magnetic moment. For example, t h e moments increase with decreasing coordination number and increasing interatomic distance. Our results will be compared with available experimental and theoretical results

Magnetism in small vanadium clusters

Journal ArticleUsing the self-consistent-field molecular-orbital theory and the density-functional approximation, we show that vanadium could become magnetic if its size and dimension were constrained. This is illustrated for vanadium forming clusters with body-centered-cubic (bcc) geometry as well as for linear chains. The magnetic moment of the bcc clusters is found to vanish abruptly as the size increases, while the clusters always retain their moment in the linear-chain configurations. The moments are also found to be finite for large interatomic spacings irrespective of the cluster topology, and tend to vanish when the interatomic distances are reduced. The results are explained by using a simple Stoner criterion

Magnetism of Al-Mn quasicrystals

Journal ArticleThe effect of symmetry and concentration of Mn on the magnetism of Al-Mn quasicrystals has been investigated through self-consistent density-functional calculations using molecular clusters and supercell band-structure schemes. A single Mn atom surrounded by 54 Al atoms in an icosahedral or a cuboctahedral structure is found to be nonmagnetic. However, as the Mn concentration is increased, moments develop on Mn sites whose magnitude and coupling depend on their location

A Public Choice Theory of Criminal Procedure

We provide a more persuasive justification for the pro-defendant bias in Anglo-American criminal procedure than the most commonly forwarded justifications to date. The most commonly forwarded rationale for the pro-defendant bias is that the costs of false convictions – specifically, the sanctioning and deterrence costs associated with the erroneous imposition of criminal sanctions – are greater than the costs of false acquittals. We argue that this rationale provides at best a partial justification for the extent of pro-defendant procedural rules. Under our alternative justification, pro-defendant protections serve primarily as constraints on the costs associated with improper enforcement or rent seeking in the law enforcement process. The theory developed here explains key institutional features of Anglo-American criminal procedure and provides a positive theory of the case law as well. The theory is also corroborated by empirical evidence on corruption from several countries

Magnetic coupling in neutral and charged Cr-2, Mn-2, and CrMn dimers

Theoreticalab initio studies of neutral, cationic and anionic Cr2, Mn2, and CrMn dimers have been carried out to explore the progression of magnetic coupling with the number of electrons. It is shown that while Cr2 and Cr−2 have antiferromagnetically coupled atomic spins, Cr+2 has a ferromagneticground state closely followed by an antiferromagnetic state. On the other hand, all Mn2 dimers are ferromagnetic, irrespective of the charge. The neutral CrMn is ferrimagnetic while the charged CrMn are antiferromagnetic. In all cases, the charged dimers are found to be more stable than the neutral ones. The results are compared with available calculations and experiments and the difficulties associated with theoretical description and the experimental interpretations are discussed

An ab initio investigation on the endohedral metallofullerene Gd 3 N – C 80

First-principles electronic structure studies on the ground state geometry and electronic and magnetic properties of bare and hydrogen coated metallofullerene Gd3N–C80 have been carried out within a density functional formalism. The correlation effects are incorporated either through a generalized gradient corrected functional or through an on-site Coulomb interaction (LDA+U). It is shown that the bare Gd3N–C80 possess a ferromagnetic ground state with a large spin moment of 21μB that is highly stable against spin fluctuations. The simulated Raman spectrum shows that the low-energy peaks are contributed by the floppy movement of N atom. As to the effect of addition of hydrogens, it is shown that the most favorable site for the hydrogen adsorption is an on-top site where the H atom is located above a five-member carbon ring with a binding energy of 1.92eV, while the least stable site corresponds to an on-top absorption above a six-member ring. A study of the energetics upon multiple adsorption of H shows that the binding energy of the H to metallofullerene drops after 11 H atoms. This shows that it should be possible to attach multiple ligands offering the potential that the Gd3N–C80 can be functionalized with ligands or assembled in cluster assemblies