Collective Strategy Condensation: When Envy Splits Societies

Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed.     

High-energy x-ray diffraction study on phase transition asymmetry of plastic crystal neopentylglycol

As a prototype material of colossal barocaloric effects, neopentylglycol is investigated by combining high-precision differential scanning calorimetric measurement and high-energy x-ray diffraction measurement. The diffraction data at constant temperatures indicate a first-order phase transition with thermal hysteresis as well as the phase transition asymmetry, specifically, the phase transition is completed faster at cooling than at heating. The analysis of resulting pair distribution function confirms the intermolecular disorder in the high-temperature phase. The phase transition asymmetry is quantitatively characterized by time-resolved x-ray diffraction, which is in agreement with the thermal measurement. Also, such an asymmetry is observed to be suppressed at high pressures.     

Solid-state luminescence of Au(I) complexes with external stimuli-responsive properties

In the last decade, the field of stimuli-responsive luminescent materials have been intensely emerged because of the high potential application to functional sensors or photoelectronic devices. In particular, luminescent molecular crystals constructed from Au(I) complexes have produced a wide range of examples of luminescent alterations when some external stimulations, such as heat, mechanical stress, vapor (or solvents), were applied to the solid samples. In this review, we describe the recent progress through a summary of the reported Au(I) complexes based on their utilized stimuli-responsive mechanisms, which are categorized in crystal phase transitions (“crystal-to-amorphous”, “crystal-to-crystal” and “single-crystal-to-single-crystal” transitions) and molecular rotation in crystalline media, respectively.     

Pressure-induced novel structure with graphene-like boron-layer in titanium monoboride

The recent discovery of the novel boron-framework in boron-rich metal borides with complex structures and intriguing features under high pressure has stimulated the search into the unique boron-network in the metal monoborides or boron-deficient metal borides at high pressure. Herein, based on the particle swarm optimization algorithm combined with first-principles calculations, we thoroughly explored the structural evolution and properties of TiB up to 200 GPa. This material undergoes a pressure-induced phase transition of $Pnma$ $\to $ $Cmcm$ $\to $ $Pmmm$. Besides of two known phases $Pnma$ and $Cmcm$, an unexpected orthorhombic $Pmmm$ structure was predicted to be energetically favored in the pressure range of 110.88-200 GPa. Intriguingly, the B covalent network eventually evolved from a one-dimensional zigzag chain in $Pnma$-TiB and $Cmcm$-TiB to a graphene-like B-sheet in $Pmmm$-TiB. On the basis of the microscopic hardness model, the calculated hardness ($H_{\rm v}$) values of $Pnma$ at 1 atm, $Cmcm$ at 100 GPa, and $Pmmm$ at 140 GPa are 36.81 GPa, 25.17 GPa, and 15.36 GPa, respectively. Remarkably, analyses of the density of states, electron localization function and the crystal orbital Hamilton population (COHP) exhibit that the bonding nature in the three TiB structures can be considered as a combination of the B-B and Ti-B covalent interactions. Moreover, the high hardness and excellent mechanical properties of the three TiB polymorphs can be ascribed to the strong B-B and Ti-B covalent bonds.     

三核过渡金属配合物在催化反应中的研究进展

多核过渡金属配合物作为一类广泛应用的均相催化剂,其设计灵感往往来自天然酶的多金属活性位点所发挥的重要作用.目前,三核金属配合物作为活化小分子的多金属催化剂受到了广泛的关注.为深入理解三核过渡金属配合物在催化反应中作用特点,对近年报道的代表性三核过渡金属配合物按金属中心进行分类,并对配体环境形成特点及催化应用进行综述.从金属中心出发,讨论了三核过渡金属配合物的几何结构和电子特征;从配体环境出发,总结了关联三个独立的金属位点的配位环境特征;在催化应用方面,重点综述了三核过渡金属配合物在涉及特定化学键活化反应的催化作用机制,最后对三核过渡金属配合物的催化应用前景进行展望.     

Mo掺杂NiMnSe2的制备及其超级电容器性能

成分和结构是影响多元过渡金属硒化物电化学活性的关键因素。适当掺杂其他金属元素可以有效提高电极材料的电化学性能。通过简单的一步水热法,在泡沫镍上制备出了一种无黏结剂的Mo掺杂NiMnSe₂(记作Ni_0.8Mo_0.2MnSe₂)。Mo的少量掺杂为电极材料提供了丰富的反应活性位点,大大提高了NiMnSe₂的电化学性能。在1 A·g^-1时,Ni_0.8Mo_0.2MnSe₂的比容量达到1 404.0 F·g^-1。掺杂Mo显著降低了NiMnSe₂的电荷转移电阻和扩散电阻。组装的混合超级电容器Ni_0.8Mo_0.2MnSe₂//AC (活性炭)比容量达到81.6 F·g^-1,且倍率性能优异。在2 A·g^-1下连续充放电10 000周,容量保持率为95.8%,表现出超高的循环稳定性。混合超级电容器Ni_0.8Mo_0.2MnSe₂//AC在376.6 W·kg^-1的功率密度下,能量密度达25.5 Wh·kg^-1,高于NiMnSe₂//AC (17.3 Wh·kg^-1)。     

Transition Metal-Free Aromatic C−H,C−N,C−S and C−O Borylation

Aromatic organoboron compounds are highly valuable building blocks in organic chemistry. They were mainly synthesized through aromatic C−H and C−Het borylation, in which transition metal-catalysis dominate. In the past decade, with increasing attention to sustainable chemistry, numerous transition metal-free C−H and C−Het borylation transformations have been developed and emerged as efficient methods towards the synthesis of aromatic organoboron compounds. This account mainly focuses on recent advances in transition metal-free aromatic C−H, C−N, C−S, and C−O borylation transformations and provides insights to where further developments are required.     

Investigating the Mechanism by Which Intragap States Tailor Light Emission: Case of Copper Deficient and Zn Doped Cu−In−Se Quantum Dots**

The large structural tolerance of I–III–VI group quantum dots (QDs) to off-stoichiometry allows their photoluminescence properties to be adjusted via doping, thereby enabling application in different fields. However, the photophysical processes underlying their photoluminescence mechanism remain significantly unknown. In particular, the transition channels of CuInSe₂ QDs, which are altered by intrinsic and extrinsic intragap states, remain poorly reported. Herein, we investigated the photophysical processes associated with intragap states via electrochemical and optical techniques by using copper deficient Cu−In−Se QDs as well as Zn doped Cu−In−Se QDs. When the Cu/In molar ratios of Cu−In−Se QDs increased from 0.3 : 1 to 0.9 : 1, the photoluminescence spectra displayed a red-shift from 700 nm to 1050 nm. Although there was a blue-shift after the introduction of Zn²⁺ dopants in Cu−In−Se QDs, a significant red-shift occurred (from 660 nm to 760 nm) when the Zn/Cu molar ratios decreased from 0.7 : 0.3 to 0.3 : 0.7. The Gaussian deconvolution results of the photoluminescence spectra and the band gap derived from absorption spectra by fitting supported the fact that the optical transition channels are dependent on the Cu/In and Zn/Cu molar ratios. After the introduction of the Zn²⁺ ions, the alloyed-resultant blue-shift of the emission spectra was observed, primarily due to the enlarged band gap; however, the radiative recombination of prominent intrinsic intragap states is still observed; and only a small proportion of the band-edge exciton undergoes recombination for the sample with low Zn content. Cyclic voltammetry measurements revealed well-defined extrinsic Zn_Cu intragap states (Zn substitution on Cu sites) and intrinsic Cu^x (x= 1+/2+) states in the band gap. The results presented here provide a better understanding of the varying effects of dopant on photoluminescence in terms of I–III–VI group QDs.