Exploring configurations and properties of boron carbide by first principle

Abstract

Based on the first principle, the formation energy, phonon vibration, physical property of three common B 4 C models were extensively study. Through the calculation of thermodynamic formation energy, it is confirmed po model has the most stable energy configuration. Combined the simulated x-ray and experimental data, it is found that the experimental boron carbide is actually composed of a variety of configurations, the majority of which is po model. Via the analysis of phonon vibration, the highest phonon frequencies of the different configurations were identified as the result of stretching vibrations from the triatomic chain. The research of electrical properties of three B 4 C models clarify B 4 C is a semiconductor but will transform to conductor at specific high pressure. The calculation of the mechanical property states that B 4 C is hard material while the hardness will gradually decrease with pressure increases. Both the relationship of their electrical properties and mechanical properties with pressure illustrate that the po model has the fastest structural change and ch model has the slowest change.

A DFT study of structural and electronic properties of some B12-based compounds under hydrostatic pressure

“…In the case of B 12 C 3 , a 3-atom chain of boron or carbon is formed, and the two chain-end atoms are bonded to the equatorial atoms located on six neighboring icosahedra. Different chain configurations can be taken into account when calculating the physical properties of B 12 C 3 theoretically [14]. In this work, since we will consider the structural and electronic properties of some boron-rich compounds comparatively with each other, the B 12 C 3 structure will be taken as the The binding characterization of B 12 -based compounds consisting of B 12 icosahedra forming the boron skeleton structure and the effect of this characterization on physical properties have been intensively investigated for a long time.…”

“…Different bond interactions between icosahedral and chain atoms in boron-rich compounds provide these compounds with unusual electronic properties. In the literature, there are many studies investigating the electronic structures of α-B 12 [4,[15][16][17][18], B 12 O 2 [19,20], B 12 P 2 [6,21], B 12 As 2 [10,22,23], B 12 C 3 [14,24,25], B 13 C 2 [2,26,27] and B 13 N 2 [5,28] compounds using the first principles method. Standard density functional theory(DFT) computations generally calculate the electronic band gap of materials to be smaller than the optical band (experimental) gap [29].…”

First principles study of post-boron carbide phases with icosahedra broken*

“…Boron carbide (B 4 C), as the third hardest material next to diamond and cubic boron nitride, has remarkable mechanical properties such as large elastic moduli including bulk modulus, shear modulus and Young's modulus, [1,2] large fracture toughness and flexure strength, [1,3,4] high hardness, [3][4][5] high Hugoniot elasitc limit (HEL 15 GPa-20 GPa), [6] which make B 4 C possess numerous applications in military and industry areas, with the B 4 C serving as tank armor, bulletproof vests, wear-resistant, and cutting tool material, etc. [7][8][9] However, experimental dynamics on B 4 C shows that its resistance against higher velocity threats was severe discounted.…”

“…[18][19][20] Amorphization or phase transition depends strongly on degree of non-hydrostatic pressure in DAC, [21,22] or scratching and nanoindentation. [23][24][25][26] The amorphization of B 4 C is associated with the destruction of the C-B-C chains, sp 2 -bonded aromatic carbon clusters formed and amorphous boron clusters created by dynamic indentation. [25,26] Previous studies have pointed that the bending of the chain with the intermediate atoms of the chain bonding to the adjacent icosahedral atoms plays a very dominant role in the stress-induced amorphization of B 4 C, and the icosahedra appear more stable than the linear chain under high pressures.…”