Grochala Wojciech
Centre for New Technologies, The University of Warsaw, Zwirki i Wigury 93, 02089 Warsaw, Poland.
Phys Chem Chem Phys. 2017 Nov 29;19(46):30984-31006. doi: 10.1039/c7cp05027e.
Building on Part 1 devoted to atoms and molecules (PCCP, in press 2017), we now focus on the crystal structure and electronic properties of solids as viewed from the Maximum Hardness Principle (MHP), first formulated by Pearson in 1987. The focus is on cases where nuclear potential acting on electrons does not remain constant and where substantial modifications of the nuclear geometry take place (Generalized MHP, GMHP). We present an overview of important manifestations of the (G)MHP for solids such as (i) a tendency of metals and doped-semiconductors to undergo superconducting transition at low temperatures, (ii) propensity of many types of alloys to develop a band gap or a pseudo-gap, (iii) preference for preserving the noble gas (octet, doublet) configuration of main block element ions in the solid state, (iv) preference of Jahn-Teller systems for band-gap-opening vibronic-coupling-related lattice distortions, (v) pressure phenomena leading to localization of the electronic density, (vi) tendency to annihilate the null band gap via phase separation (while preserving the nominal chemical composition), (vii) absence of a large number of families of high-T superconductors, (viii) resistance of most stable systems to chemical doping, etc. GMHP turns out to be an important qualitative guide in studies of solid state polymorphism and electronic phenomena. Exceptions from (G)MHP are discussed, and a more restrictive formulation of the principle is proposed.
基于第一部分对原子和分子的讨论（《物理化学化学物理》，2017年即将出版），我们现在从1987年由皮尔逊首次提出的最大硬度原理（MHP）的角度，聚焦于固体的晶体结构和电子性质。重点关注作用于电子的核势并非恒定不变以及核几何结构发生实质性改变的情况（广义MHP，GMHP）。我们概述了（G）MHP在固体中的重要表现，例如：（i）金属和掺杂半导体在低温下发生超导转变的趋势；（ii）许多类型合金形成带隙或赝隙的倾向；（iii）固态中主族元素离子倾向于保持稀有气体（八隅体、二隅体）构型；（iv） Jahn - Teller体系倾向于与带隙打开相关的电子 - 振动耦合晶格畸变；（v）导致电子密度局域化的压力现象；（vi）通过相分离消除零带隙的趋势（同时保持名义化学成分）；（vii）大量高温超导体系的缺失；（viii）大多数稳定体系对化学掺杂的抗性等。结果表明，GMHP在固态多晶型和电子现象的研究中是一个重要的定性指导。我们讨论了（G）MHP的例外情况，并提出了该原理的一个更具限制性的表述。
