http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Perspective: Theory and simulation of hybrid halide perovskites
Whalley, Lucy D.,Frost, Jarvist M.,Jung, Young-Kwang,Walsh, Aron American Institute of Physics 2017 The Journal of chemical physics Vol.146 No.22
<P>Organic-inorganic halide perovskites present a number of challenges for first-principles atomistic materials modeling. Such “plastic crystals” feature dynamic processes across multiple length and time scales. These include the following: (i) transport of slow ions and fast electrons; (ii) highly anharmonic lattice dynamics with short phonon lifetimes; (iii) local symmetry breaking of the average crystallographic space group; (iv) strong relativistic (spin-orbit coupling) effects on the electronic band structure; and (v) thermodynamic metastability and rapid chemical breakdown. These issues, which affect the operation of solar cells, are outlined in this perspective. We also discuss general guidelines for performing quantitative and predictive simulations of these materials, which are relevant to metal-organic frameworks and other hybrid semiconducting, dielectric and ferroelectric compounds.</P>
Whalley, Lucy D.,Skelton, Jonathan M.,Frost, Jarvist M.,Walsh, Aron American Physical Society 2016 Physical Review B Vol.94 No.22
<P>Lattice vibrations in CH3NH3PbI3 are strongly interacting, with double-well instabilities present at the Brillouin zone boundary. Analysis within a first-principles lattice-dynamics framework reveals anharmonic potentials with short phonon quasiparticle lifetimes and mean free paths. The phonon behavior is distinct from the inorganic semiconductors GaAs and CdTe where three-phonon interaction strengths are three orders of magnitude smaller. The implications for the applications of hybrid halide perovskites arising from thermal conductivity, band-gap deformation, and charge-carrier scattering through electron-phonon coupling, are presented.</P>
The Yuan and Shanghai Pilot Free Trade Zone
( Daqing Yao ),( John Whalley ) 세종대학교 경제통합연구소(구 세종대학교 국제경제연구소) 2015 Journal of Economic Integration Vol.30 No.4
In this paper, we present evidence as to the effects of the China (Shanghai) Pilot Free Trade Zone on China’s capital controls which was initiated in September, 2013. It was a trial to introduce a combination of floating exchange rate and capital account liberalization into China’s macro policy mix. We employ three methods to test the China (Shanghai) Pilot Free Trade Zone’s impact on capital controls: price spread tests between Chinese Yuan in Hong Kong and Chinese Yuan, Renminbi yield gaps between onshore and offshore Renminbi markets, and Granger causalities in China’s money supply and foreign interest rates. All these tests give consistent results suggesting that the impact of China’s capital controls is weaker since the China (Shanghai) Pilot Free Trade Zone.
Endogenous Effort and Intersectoral Labour Transfers Under Industrialization
( Madanmohan Ghosh ),( John Whalley ) 세종대학교 경제통합연구소 2007 Journal of Economic Integration Vol.22 No.3
This paper takes as its point of departure the claim in the literature that strong Asian growth performance is accounted for largely by the accumulation of factor inputs (financial savings and human capital accumulation). This stands in sharp contrast to Polanyi`s (1944) interpretation of European growth being a “great transformation” from an agricultural to an industrial economy. Our objective is to find models in which intersectoral transfers in Asia do account for significant portions of observed growth performance, besides factor input growth and residually calculated productivity growth. We begin with traditional Lewis models, where an efficiency gain results from transferring labour from the traditional (family based) agricultural sector, in which labour receives its average product, to the modern (industrial) sector in which labourers are paid their marginal product. We show that as one moves closer to Pareto Optimality in this system (say by taxing the traditional sector`s output), there is a gain but this is typically small. We then formulate Lewis type models in which the product of effort and labour enters each sector`s production function, and individuals in the traditional sector only receive a fraction of the return to their incremental effort due to average product pricing of labour. In this case, the level of effort in each sector, is endogenously determined along with the intersectoral allocation of labour, since the representative household is modeled as having a utility function defined over goods along with the disutility of effort. Differences in effort levels across sectors support accompanying differences in average and marginal products of labour. We use this model to analyze growth processes in Thailand and South Korea over the period between the 1960s and 1990s. Results suggest significant contributions to growth from intersectoral labour transfers in Lewis models with endogenous effort, and negligible contributions from models without endogenous effort.
Conductance and Geometry of Pyridine-Linked Single-Molecule Junctions
Kamenetska, M.,Quek, Su Ying,Whalley, A. C.,Steigerwald, M. L.,Choi, H. J.,Louie, Steven G.,Nuckolls, C.,Hybertsen, M. S.,Neaton, J. B.,Venkataraman, L. American Chemical Society 2010 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.132 No.19
<P>We have measured the conductance and characterized molecule−electrode binding geometries of four pyridine-terminated molecules by elongating and then compressing gold point contacts in a solution of molecules. We have found that all pyridine-terminated molecules exhibit bistable conductance signatures, signifying that the nature of the pyridine−gold bond allows two distinct conductance states that are accessed as the gold−molecule−gold junction is elongated. We have identified the low-conductance state as corresponding to a molecule fully stretched out between the gold electrodes, where the distance between contacts correlates with the length of the molecule; the high-conductance state is due to a molecule bound at an angle. For all molecules, we have found that the distribution of junction elongations in the low-conductance state is the same, while in the high-conductance state, the most likely elongation length increases linearly with molecule length. The results of first-principles conductance calculations for the four molecules in the low-conductance geometry agree well with the experimental results and show that the dominant conducting channel in the conjugated pyridine-linked molecules is through the π* orbital.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2010/jacsat.2010.132.issue-19/ja1015348/production/images/medium/ja-2010-015348_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja1015348'>ACS Electronic Supporting Info</A></P>
Ousaka, Naoki,Grunder, Sergio,Castilla, Ana M.,Whalley, Adam C.,Stoddart, J. Fraser,Nitschke, Jonathan R. American Chemical Society 2012 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.134 No.37
<P>A series of large, optically active Fe<SUB>4</SUB>L<SUB>6</SUB> cages was prepared from linear 5,5′-bis(2-formylpyridines) incorporating varying numbers (<I>n</I> = 0–3) of oligo-<I>p</I>-xylene spacers, chiral amines, and Fe<SUP>II</SUP>. When a cage was constructed from the ligand bridged by one <I>p</I>-xylene spacer (<I>n</I> = 1) and a bulky chiral amine, both a homochiral Fe<SUB>2</SUB>L<SUB>3</SUB> helicate and Fe<SUB>4</SUB>L<SUB>6</SUB> cage were observed to coexist in solution due to a delicate balance between steric factors. In contrast, when a less bulky chiral amine was used, only the Fe<SUB>4</SUB>L<SUB>6</SUB> cage was observed. In the case of larger cages (<I>n</I> = 2, 3), long-range (>2 nm) stereochemical coupling between metal centers was observed, which was minimally diminished as the ligands were lengthened. This communication was mediated by the ligands’ geometries and rigidity, as opposed to gearing effects between xylene methyl groups: the metal-centered stereochemistry was not observed to affect the axial stereochemistry of the ligands.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2012/jacsat.2012.134.issue-37/ja306615d/production/images/medium/ja-2012-06615d_0014.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja306615d'>ACS Electronic Supporting Info</A></P>
Intrinsic doping limit and defect-assisted luminescence in Cs4PbBr6
Jung, Young-Kwang,Calbo, Joaquí,n,Park, Ji-Sang,Whalley, Lucy D.,Kim, Sunghyun,Walsh, Aron The Royal Society of Chemistry 2019 Journal of Materials Chemistry A Vol.7 No.35
<P>Cs4PbBr6 is a member of the extended halide perovskite family that is built from isolated (zero-dimensional) PbBr6<SUP>4−</SUP> octahedra with Cs<SUP>+</SUP> counter ions. The material exhibits anomalous optoelectronic properties: optical absorption and weak emission in the deep ultraviolet (310-375 nm) with efficient luminescence in the green region (∼540 nm). Several hypotheses have been proposed to explain the giant Stokes shift including: (i) phase impurities; (ii) self-trapped exciton; (iii) defect emission. We explore, using first-principles theory and self-consistent Fermi level analysis, the unusual defect chemistry and physics of Cs4PbBr6. We find a heavily compensated system where the room-temperature carrier concentrations (<10<SUP>9</SUP> cm<SUP>−3</SUP>) are more than one million times lower than the defect concentrations. We show that the low-energy Br-on-Cs antisite results in the formation of a polybromide (Br3) species that can exist in a range of charge states. We further demonstrate from excited-state calculations that tribromide moieties are photoresponsive and can contribute to the observed green luminescence. Photoactivity of polyhalide molecules is expected to be present in other halide perovskite-related compounds where they can influence light absorption and emission.</P>