Systematic Enumeration of Low‐Energy Graphyne Allotropes Based on a Coordination‐Constrained Searching Strategy

Abstract

The discovery of graphene has opened a new research space into 2D carbon materials and has gained tremendous scientific attention about their fundamental properties and potential applications. [1-6] Up to now, numerous 2D carbon allotropes have been proposed and investigated, for instance, pentaheptites R 57-1 and R 57-2 , [7,8] Haeckelite sheets H 567 and O 567 , [8] octite SC, [9] SW-graphene, [10,11] Ψ-graphene, [12,13] T-graphene, [14] POgraphene, [15,16] HOP-graphene, [17] and pha-graphene. [18] These unique 2D carbon allotropes provide rich material platforms for designing and fabricating optoelectronic devices and realizing novel topological phenomena. [10,11,18] Among 2D carbon systems, the graphynes containing both sp and sp 2 hybridized carbon atoms form one of the biggest branches of graphene allotropes. [19] Early in 1987, this low-energy layered phase of carbon was predicted to be of hightemperature kinetic stability by Baughman. [20] The successful synthesis of γ-graphdiyne, β-graphdiyne, carbon ene-yne, and their derivants in experiments further inspired interest in such sp-sp 2 hybridized 2D carbon materials. [21-25] Due to the presence of acetylenic bonds associated with sp states, graphyne possesses exceptional flexibility in the geometric structure and thus exhibits many diverse allotropes, for instance, α-graphyne, β-graphyne, γ-graphyne, R-graphyne, and 6,6,12graphyne. [26-28] In addition to the various structures, fascinating physical and chemical properties have also been predicted for the graphyne family. Because of the Kekule-distortion effect, γ-graphyne and graphdiyne are semiconductors with a moderate bandgap and excellent carrier mobility. [27,29] Benefiting from the insertion of acetylenic linkages, the thermal conductance of graphyne is fundamentally lower than that of graphene, and thus leads to its preeminent thermoelectric conversion efficiency. [30-32] Due to the intrinsic hollow structures, graphyne can adsorb ions effectively or filter molecular selectively, making it a promising candidate material for electrodes or molecular sieves. [33,34] More interestingly, Dirac-cone-characterized electronic band structures are revealed not only in hexagonal graphyne (α-graphyne, [27] Pal-graphyne, [35] δ-graphyne, [36] and circumcoro-graphyne [37]), but also in orthorhombic crystal structures (β-graphyne, [27] 6,6,12-graphyne, [19] S-graphynes, [38] cp-graphyne, [39] 14,14,14-graphyne, [40] and 14,14,18-graphyne [40]).

Designing All Graphdiyne Materials as Graphene Derivatives: Topologically Driven Modulation of Electronic Properties

“…For 6-L, we find a larger relative energy than γ-GDY even if they share the same sp/sp 2 ratio value. Our results show a general qualitative agreement with ref ( 18 ). Relative energy (here with respect to graphene and in ref ( 18 ) with respect to γ-graphyne) increases with decreasing carbon densities (i.e., increasing sp/sp 2 ratio).…”

“…Our results show a general qualitative agreement with ref ( 18 ). Relative energy (here with respect to graphene and in ref ( 18 ) with respect to γ-graphyne) increases with decreasing carbon densities (i.e., increasing sp/sp 2 ratio). Our work includes some structures already investigated in the literature and several novel ones, thus revealing the wide range of possibilities available in the design of 2D sp–sp 2 carbon systems.…”

“…Early theorethical studies on GY and GDY-based system were reported in 1987 [15] and recently with modern computational methods to shed light on their properties [16][17][18]. These structures are a part of a larger family of two-dimensional π-conjugated Covalent Organic Frameworks (COF) showing the occurrence of Dirac cones [19,20], flat bands, tunable bands gap.…”

“…They can be constructed as possible modification of graphene by interconnecting sp 2 -carbon hexagons with linear sp-carbon chains of different lengths (a single or a double acetylenic bond for GY and GDY, respectively), generating new systems with peculiar and tunable electronic and optical properties. Moreover, starting from GY and GDY, many other ideal 2D hybrid sp-sp 2 carbon systems can be proposed by playing with geometry and topology offering countless possibilities in the design and tailoring of carbon allotropes, both theoretically and experimentally.Early theorethical studies on GY and GDY-based system were reported in 1987 [15] and recently with modern computational methods to shed light on their properties [16][17][18]. These structures are a part of a larger family of two-dimensional π-conjugated Covalent Organic Frameworks (COF) showing the occurrence of Dirac cones [19,20], flat bands, tunable bands gap.…”

Ground state configuration of hydrogenated Biphenylene sheet: structure, stabilities, electronic and mechanical properties from first-principles calculations

“…It is always an exciting thing to experimentally realize the theoretically predicted new crystals [1][2][3] but it is not always happen. Large numbers of new materials [4][5][6][7][8][9][10][11] have been predicted by first-principles calculations in the past decades and just few of them have been experimentally synthesized [12][13][14][15] . In the two-dimensional (2D) case, graphdiynes, Phagraphene, phosphorene and graphane are some successful stories.…”