Li Quan, Zhou Dan, Zheng Weitao, Ma Yanming, Chen Changfeng
College of Materials Science and Engineering and State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China.
Department of Physics and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154, USA.
Phys Rev Lett. 2015 Oct 30;115(18):185502. doi: 10.1103/PhysRevLett.115.185502. Epub 2015 Oct 29.
Boron-rich tungsten borides are premier prototypes of a new class of ultrahard compounds. Here, we show by first-principles calculations that their stress-strain relations display surprisingly diverse and anomalous behavior under a variety of loading conditions. Most remarkable is the dramatically changing bonding configurations and deformation modes with rising boron concentration in WB_{n} (n=2, 3, 4), resulting in significantly different stress responses and unexpected indentation strength variations. This novel phenomenon stems from the peculiar structural arrangements in tungsten borides driven by boron's ability to form unusually versatile bonding states. Our results elucidate the intriguing deformation mechanisms that define a distinct type of ultrahard material. These new insights underscore the need to explore unconventional structure-property relations in a broad range of transition-metal light-element compounds.
富含硼的硼化钨是一类新型超硬化合物的首要原型。在此，我们通过第一性原理计算表明，在各种加载条件下，它们的应力-应变关系呈现出惊人的多样和异常行为。最显著的是，随着WBₙ（n = 2、3、4）中硼浓度的增加，键合构型和变形模式发生显著变化，导致应力响应明显不同以及压痕强度出现意外变化。这一新颖现象源于硼形成异常多样键合态的能力所驱动的硼化钨中独特的结构排列。我们的结果阐明了定义一种独特类型超硬材料的有趣变形机制。这些新见解强调了在广泛的过渡金属轻元素化合物中探索非常规结构-性能关系的必要性。
