在矿氧化化物中具有低扩展性输入和开放性顺序
Philip J Camp1, Amparo Fuertes, J Paul Attfield
1School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, United Kingdom. philip.camp@ed.ac.uk
Journal of the American Chemical Society
|March 27, 2012
概括
新的矿氧化材料表现出不同寻常的配置,取决于粒子大小. 这种"开放秩序"现象是由原子规模的混乱和局部离子排序驱动的,为新型材料结构和特性提供了潜力.
科学领域:
- 材料科学 材料科学 材料科学
- 固态化学 固态化学
- 晶体学 晶体学是指结晶学.
背景情况:
- 矿晶体结构是具有调节性质的多功能材料.
- 了解配置对于预测材料的行为和稳定性至关重要.
- 原子尺度的混乱和局部秩序显著影响宏观性质.
研究的目的:
- 预测和表征在AMO{3-z) N{-z) 氧化中不寻常的低扩展的配置.
- 探索粒子大小,原子混乱和之间的关系.
- 为了分类和理解这些材料中的"开放秩序"的性质.
主要方法:
- 配置的理论预测.
- 对晶体学秩序和局部阴离子秩序的分析.
- 应用一个通用的保林冰规则公式来计算.
- 基于"开放秩序"的氧化物的分类.
主要成果:
- 在矿氧化物中预测出不寻常的低扩展配置 (AMO(3-z) N(z)).
- 随粒子大小而变化,在宏观样本中,每个原子接近零.
- 确定了局部离子顺序 (M-N-M 键链以 90° 转) 作为亚扩张的来源.
- 将这些材料归类为具有"开放秩序"的材料,类似于铁电矿.
结论:
- 不够广泛的配置是这些无序矿氧化的关键特征.
- "开放秩序"为理解它们的独特特性提供了一个框架.
- 这些发现表明设计新型开放序列的氧化和分子结构的可能性.
- 在其他状态 (如旋转和充电) 中出现"开放顺序"现象的可能性.
相关概念视频
Third Law of Thermodynamics
A pure, perfectly crystalline solid possessing no kinetic energy (that is, at a temperature of absolute zero, 0 K) may be described by a single microstate, as its purity, perfect crystallinity,and complete lack of motion means there is but one possible location for each identical atom or molecule comprising the crystal (W = 1). According to the Boltzmann equation, the entropy of this system is zero.
Absolute Entropies and the Third Law of Thermodynamics
Ludwig Edward Boltzmann developed a definition for entropy, which stated that absolute entropy is proportional to the natural logarithm of the number of possible combinations of particles. Entropy stands alone among state functions as the only one whose absolute values can be determined.Consider a gas sample confined to a container. As the container expands, the energy levels of gas molecules become more closely spaced. This increases the number of available energy states, thereby increasing...
Entropy
Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...
Entropy
The first law of thermodynamics is quantitatively formulated via an equation relating the internal energy of a system, the heat exchanged by it, and the work done on it. A quantitative formulation of the second law of thermodynamics leads to defining a state function, the entropy.
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
When an ideal gas expands isothermally, the disorder in the gas increases. From the molecular perspective, the gas molecules have more volume to move around in.
Consider an infinitesimal step in the expansion, which...
Second Law of Thermodynamics
In the quest to identify a property that may reliably predict the spontaneity of a process, a promising candidate has been identified: entropy. Processes that involve an increase in entropy of the system (ΔS > 0) are very often spontaneous; however, examples to the contrary are plentiful. By expanding consideration of entropy changes to include the surroundings, a significant conclusion regarding the relation between this property and spontaneity may be reached. In thermodynamic models, the...
Entropy Change in Reversible Processes
In the Carnot engine, which achieves the maximum efficiency between two reservoirs of fixed temperatures, the total change in entropy is zero. The observation can be generalized by considering any reversible cyclic process consisting of many Carnot cycles. Thus, it can be stated that the total entropy change of any ideal reversible cycle is zero.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.
The statement can be further generalized to prove that entropy is a state function. Take a cyclic process between any two points on a p-V diagram.


