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This article is part of the series Nano Component 2011.

Open Access Nano Express

A one-dimensional extremely covalent material: monatomic carbon linear chain

Yaozhong Zhang1, Yanjie Su1, Liang Wang12, Eric Siu-Wai Kong1, XiaoShuang Chen2 and Yafei Zhang1*

Author Affiliations

1 Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, Research Institute of Micro/Nano Science and Technology, Shanghai Jiao Tong University, Shanghai 200240, China

2 National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China

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Nanoscale Research Letters 2011, 6:577  doi:10.1186/1556-276X-6-577

The electronic version of this article is the complete one and can be found online at: http://www.nanoscalereslett.com/content/6/1/577


Received:11 August 2011
Accepted:31 October 2011
Published:31 October 2011

© 2011 Zhang et al; licensee Springer.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Polyyne and cumulene of infinite length as the typical covalent one-dimensional (1D) monatomic linear chains of carbon have been demonstrated to be metallic and semiconductor (Eg = 1.859 eV), respectively, by first-principles calculations. Comparing with single-walled carbon nanotubes, the densities are evidently low and the thermodynamic properties are similar below room temperature but much different at the high temperature range. Polyyne possesses a Young's modulus as high as 1.304 TPa, which means it is even much stiffer than carbon nanotubes and to be the superlative strong 1D material along the axial direction. The Young's modulus of cumulene is estimated to be 760.78 GPa. In addition, polyyne is predicted to be as a one-dimensional electronic material with very high mobility.

Keywords:
carbon atomic chains; Young's modulus; heat capacity; single-walled carbon nanotubes

Introduction

Carbon nanomaterials possess different mechanical and electronic properties when the hybridization of carbon atoms changes from sp, sp2 to sp3. As quasi one-dimensional carbon nanostructures, carbon nanotubes [1], composed of sp2/sp3-hybridized carbon atoms, possess outstanding mechanical, optical, and electronic properties, offering carbon nanotubes many promising applications as composite materials and sensors, as well as technology areas such as nanoelectronics. Graphene [2], a one-atom-thick two-dimensional sheet of sp2-hybridized carbon atoms, has also attracted increasing attentions due to its excellent thermal conductivity, mechanical stiffness, and extraordinary electronic transport properties, rendering graphene potentially valuable for applications in nanoelectronics, solar cell window layers, and composite materials [3]. Among all carbon nanostructures, carbon atomic chain, comprised of monatomic linear chains of carbon atoms, is a truly one-dimensional nanomaterial and has been predicted to have extremely outstanding properties for various applications [4-6]. Recently, Zhao et al reported the experimental fabrication of monatomic carbon linear chain which was shown to be inside double-walled carbon nanotubes of 0.7 nm in diameter [4]. Three characteristic Raman shift peaks were observed in the range of 1,790 to 1,860 cm-1. Mikhailovskij et al. reported fabrication of free-standing short monatomic carbon linear chains using a developed experimental high-field technique [7]. However, desirable quantity of free-standing polyyne and cumulene samples for experimental characterization has not gotten until now.

Among various possible covalent one-dimensional (1D) monatomic linear chains of carbon, cumulene of infinite length (···C ≡ C - C···) constructed with alternate sp conjugated band and sp3 conjugated bond chain and polyyne of infinite length (···C = C = C···) with sp2 conjugated bond chain are typical rigid covalent period conjugated bond chains. Polyynes are found in interstellar molecular clouds where hydrogen is scarce. The longest reported (synthetic) polyyne to date contains 22 acetylenic units and is end-capped with triisopropylsilyl groups [8]. The polyyne of infinite length is the elusive compound called carbyne; linear acetylenic carbon is one of the carbon allotropes [9]. To date, the difference of physical properties in these two types of carbon atomic chains has not been reported. However, there is no effective method reported in the literature to synthesize and characterize free-standing carbon atomic chains. In this investigation, theoretical study of carbon atomic chains properties has been conducted. Two kinds of carbon atomic chains have been investigated by first-principles calculations. Periodic carbon atomic chain structure has been created and geometry optimized in order to build a stable structure. Thermodynamic, mechanical, and electronic properties of carbon atomic chains have been calculated, and the results of physical properties are discussed.

Calculations

First-principles calculations have been performed to investigate the physical properties of carbon atomic chains by the pseudo-potential plane wave method [10] with the generalized gradient approximation [11] of Perdew-Burke-Ernzerhof for the exchange-correlation potential [12].

For all structures, the Monkhorst-Pack scheme is used in the Brillouin zone with 2 × 2 × 10 for all the geometry optimization and total energy calculations [13]. For all relaxation calculations, the volume of cell is fixed and the structure considered are fully relaxed to accuracy where the self-consistent field was done with a convergence criterion of 2 × 10-5 eV/atom.

Since experiment data on physical properties of single-walled carbon nanotubes (SWNTs) have been extensively reported [14], the model of a (5,5) SWNT is chosen as a reference for first-principles calculation: the physical data are compared in order to confirm the accuracy of calculation method and the feasibility of carbon atomic chain.

With the reference of the distance between two neighbor layers in graphite is 3.42 Å, and linear monatomic carbon linear chain was shown to be inside double-walled carbon nanotubes of 0.7 nm in diameter, therefore, the smallest distance can be chosen as 3.42 Å between two free carbon atomic chains. The geometrical structure model of (5,5) SWNT, cumulene, and polyyne are shown in Figure 1.

thumbnailFigure 1. Geometrical structure model. (a) (5,5) SWNTs, (b) cumulene, and (c) polyyne.

The calculated geometrical model of (5,5) SWNT contains 80 carbon atoms, as shown in Figure 1a, with periodic border condition. Structural optimization has been established using a bond length of 1.42 Å, which is slight shorter than that in graphene inducing from the surface curving of the SWNT. The model of cumulene as shown in Figure 1b is built with 12 carbon atoms with alternate sp conjugated band and sp3 bonds and periodic border condition. The length of sp conjugated bond is 0.1264 nm and that of sp3 bond is 0.1476 nm. Polyyne is in the same set as cumulene, as shown in Figure 1c with 12 carbon atoms, and there are only sp2 conjugated bond of length up to 0.1404 nm with periodic border condition.

Results and discussion

The calculated data of (5,5) SWNT, cumulene, and polyyne are listed in Table 1 in which diamond and graphene are included for comparing. At first, the structure stability of cumulene and polyyne is demonstrated to be lower than SWNT because their Gibbs free energy is more minus than that of (5,5) SWNT. Secondly, SWNT has been known as a super light one-dimensional material. However, cumulene and polyyne have even much lower density for potential applications as typical one-dimensional carbon materials.

Table 1. Calculated data of (5,5) SWNT, cumulene, and polyyne

It has been reported that the experimental Young's modulus of (5,5) SWNT is about 0.3 to 0.6 TPa with zero bandgap [15,16]. The calculated Young's modulus of SWNTs in this investigation is 805.12 GPa, which is quite close to the experiment data, demonstrating the successful application of the first-principles theory to calculate the mechanical properties of carbon nanoscale structures. The mechanical properties and bandgap energy of (5,5) SWNTs and carbon atomic chains are listed in Table 1.

The calculated Young's modulus of polyyne is as high as 1,304.19 GPa, which is much larger than that of (5,5) SWNTs, cumulene (760.78 GPa), or any known materials. The high Young's modulus of polyyne can be attributed to the high strength of sp2 conjugated bonds. We note, however, that in the SWNT structure, the carbon bonds may be considered as a hybrid spx (2 < x < 3) bond, which is much weaker than sp2 conjugated bond. In the cumulene structure, there exists the single sp3 bond, which is even weaker than the spx (2 < x < 3) bond in SWNT structure. Therefore, we conclude that polyyne possesses the highest strength along its axial compared to any other materials.

The calculation results show that cumulene is a semiconductor (Eg = 1.859 eV), but polyyne is metallic. As we know, the electronic conductivity of carbon structures comes from enlarged moving range of electrons through sp2 conjugated bonds, which decrease the system energy level and result in the effect of the electron mobility increasing significantly [17-20]. Because of a single sp3 carbon bond in the cumulene structure, the electronic conductivity is much lower than that of polyyne, and the bandgap energy of cumulene widens and renders cumulene to be a semiconductor.

The specific heat capacity chart of cumulene in Figure 2 shows that heat capacity increases with increasing temperature. According to the thermal equation:

thumbnailFigure 2. Specific heat capacity sketch of cumulene, polyyne and (5,5) SWNT.

<a onClick="popup('http://www.nanoscalereslett.com/content/6/1/577/mathml/M1','MathML',630,470);return false;" target="_blank" href="http://www.nanoscalereslett.com/content/6/1/577/mathml/M1">View MathML</a>

(1)

where K is the coefficient of heat conductivity, c is specific heat capacity, m is mass, and X replaces other parameters. Specific heat capacity is proportional to heat capacity; therefore, the coefficient of heat conductivity is proportional to heat capacity [21]. It can be noticed that the heat conductivity coefficient of cumulene increases with rising temperature.

SWNT is a one-dimensional super low-density material, with very high Young's modulus. In this investigation, the heat capacity chart is calculated and shows a trend rises with increasing temperature gradually, as shown in Figure 2. Comparing at 300 K, the specific heat capacities of cumulene, polyyne, and (5,5) SWNT are about 1.307, 1.162, and 0.174 J g-1 K-1, respectively. The specific heat capacity of (5,5) SWNT is about an order smaller than that of the cumulene and polyyne. Meanwhile, the increasing rate of the specific heat capacity of (5,5) SWNT is slower grading as the temperature increases from 300 K. These results indicate that the thermodynamic properties of cumulene and polyyne are different obviously from that of SWNTs. SWNT has been known as a super one-dimensional material with very high Young's modulus and low density for application in many fields. However, cumulene and polyyne have even much lower density and extremely high Young's modulus for some potential applications.

On the other hand, low-dimensional carbon materials, such as carbon nanotubes and graphene, have been reported to have very high mobility values of 100,000 cm2/V·s [22] and 200,000 cm2/V·s [23] at room temperature, respectively. The reason for such high mobility is related to the carbon structure of spx conjugation. For example, graphite with similar carbon structure is a good conductor of electricity. The mobility of charges in graphite is as high as 20,000 cm2/V·s at room temperature. Graphite is also strong, lightweight, and an excellent conductor of heat. The mobilities in nanotubes and graphenes turn out to be even higher than in graphite because low-dimensional carbon structures of spx conjugation behave as high-mobility electron gases. Another reason may lie in the quantum confinement nature of the low-dimensional carbon structure, which is harder to scatter electrons in low-dimensional confined structure. According to the typical structure of polyyne, it has the most favorable quantum confined carbon structure of spx conjugation for possessing a possible super high electron mobility and super conductivity as well. However, cumulene may have a relatively lower electron mobility due to its sp conjugated band and sp3 bond alternate chain structure. Electrons can only go forward or backward but not sideways. Metallic carbon atomic chains can behave as one-dimensional electron gases, having outstanding properties in bandgap energy as well as Young's modulus. Indeed, the results of this investigation suggest that monatomic carbon linear chains, cumulene and polyyne, have promising potential application in many fields.

Conclusions

First-principles calculations have been performed to investigate the properties of covalent one-dimensional (1D) monatomic linear chains of carbon. Polyyne and cumulene of infinite length, as the two typical chains, have been studied with SWNT, graphene, and diamond to reveal the fundamental and technologically interesting features. The Young's modulus of polyyne has been demonstrated to be high as 1.304 TPa, which is even much higher than that of (5,5) SWNT (0.805 TPa) and diamond (1.050 TPa). This means that polyyne is an extremely strong 1D material along the axial direction. Specific heat capacity analysis shows that the thermodynamic properties of cumulene and polyyne are different obviously from those of SWNTs and that cumulene and polyyne have much larger specific heat capacity. According to the typical electronic structure of polyyne, a super high electron mobility is predicted to exist in the most favorable quantum confined electron gas structure in 1D. Cumulenes as a semiconductor (Eg ≈ 1.859 eV) and polyynes as a metallic monatomic chains are distinguished from other organic chains by their rigidity, which makes them promising for applications in nanotechnology.

Competing interests

The authors declare that they have no competing interests.

Authors' contributions

YZ carried out the study and drafted the manuscript. YS participated in the sequence alignment. LW participated in the design of the study and sequence alignment. ESK participated in the sequence alignment. XC participated in the sequence alignment. YZ participated in the design of the study and sequence alignment.

Acknowledgements

We acknowledge the financial supports from National Natural Science Foundation of China (no. 50730008, 61006002), Shanghai Science and Technology Grant (no. 1052nm02000), and the support from the U-M/SJTU Collaborative Research Program in Renewable Energy Science and Technology.

References

  1. Iijima S: Helical microtubules of graphitic carbon.

    Nature 1991, 354:56. Publisher Full Text OpenURL

  2. Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, Grigorieva IV, Firsov AA: Electric field effect in atomically thin carbon films.

    Science 2004, 305:666. OpenURL

  3. Pierson HO: Handbook of Carbon, Graphite, Diamond, and Fullerenes: Properties, Processing, and Applications [B]. Berkshire: Noyes Publication; 1993.

    ISBN: 0-8155-1339-9

  4. Zhao XL, Ando Y, Liu Y, Jinno M, Suzuki T: Carbon nanowire made of a long linear carbon chain inserted inside a multiwalled carbon nanotube.

    Phys Rev Lett 2003, 90:187401. PubMed Abstract | Publisher Full Text OpenURL

  5. Muramatsu H, Hayashi T, Kim YA, Shimamoto D, Endo M, Terrones M, Dresselhaus MS: Synthesis and isolation of molybdenum atomic wires.

    Nano Lett 2008, 8:237. PubMed Abstract | Publisher Full Text OpenURL

  6. Kitaura R, Nakanishi R, Saito T, Yoshikawa H, Awaga K, Shinohara H: High-yield synthesis of ultrathin metal nanowires in carbon nanotubes.

    Angew Chem Int Ed 2009, 48:8298. Publisher Full Text OpenURL

  7. Mikhailovskij IM, Wanderka N, Ksenofontov VA, Mazilova TI, Sadanov EV, Velicodnaja OA: Preparation and characterization of monoatomic C-chains: unraveling and field emission.

    Nanotechnology 2007, 18:475705. Publisher Full Text OpenURL

  8. Chalifoux WA, Tykwinski RR: Synthesis of polyynes to model the sp-carbon allotrope carbine.

    Nature Chemistry 2010, 2:967. PubMed Abstract | Publisher Full Text OpenURL

  9. Chalifoux WA, Tykwinski RR: Synthesis of extended polyynes: Toward carbine.

    C R Chimie 2009, 12:341. Publisher Full Text OpenURL

  10. Perdew JP, Chevary JA, Vosko SH, Jackson KA, Pederson MR, Singh DJ, Fiolhais C: Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation.

    Phys Rev B 1992, 46:6671. Publisher Full Text OpenURL

  11. Vanderbilt D: Soft self-consistent pseudopotentials in a generalized eigenvalue formalism.

    Phys Rev B 1990, 41:7892. Publisher Full Text OpenURL

  12. Perdew JP, Berke K, Ernzerhof M: Generalized gradient approximation made simple.

    Phys Rev Lett 1996, 77:3865. PubMed Abstract | Publisher Full Text OpenURL

  13. Monkhorst HJ, Pack JD: Special points for Brillouin-zone integrations.

    Phys Rev B 1976, 13:5188. Publisher Full Text OpenURL

  14. Lu JP: Elastic properties of carbon nanotubes and nanoropes.

    Phys Rev Lett 1997, 79:1297. Publisher Full Text OpenURL

  15. Pan ZW, Xie SS, Lu L, Chang BH, Sun LF, Zhou WY, Wang G, Zhang DL: Tensile tests of ropes of very long aligned multiwall carbon nanotubes.

    Appl Phys Lett 1999, 74:3152. Publisher Full Text OpenURL

  16. Jorio A, Saito R, Hafner JH, Lieber CM, Hunter M, McClure T, Dresselhaus G, Dresselhaus MS: Structural (n,m) Determination of isolated single-wall carbon nanotubes by resonant raman scattering.

    Phys Rev Lett 2001, 86:1118. PubMed Abstract | Publisher Full Text OpenURL

  17. Chiang CK, Fincher CB Jr, Park YW, Heeger AJ, Shirakawa H, Louis EJ, Gau SC, MacDiarmid AG: Conducting polymers: halogen doped polyacetylene.

    Phys Rev Lett 1977, 39:1098. Publisher Full Text OpenURL

  18. Chiang CK, Park YW, Heeger AJ, Shirakawa H, Louis EJ, MacDiarmid AG: Electrical conductivity in doped polyacetylene.

    J Chem Phys 1978, 69:5098. Publisher Full Text OpenURL

  19. Fincher CR Jr, Peebles DL, Heeger AJ, Druy MA, Matsumura Y, MacDiarmid AG, Shirakawa H, Ikeda S: Anisotropic optical properties of pure and doped polyacetylene.

    Solid State Commun 1978, 27:489. Publisher Full Text OpenURL

  20. Park YW, Druy MA, Chiang CK, MacDiarmid AG, Heeger AJ, Shirakawa H, Ikeda S: Anisotropic electrical conductivity of partially oriented polyacetylene.

    J Polym Sci Part C- Polym Lett 1979, 17:195. OpenURL

  21. Zhang YZ, Zhao B, Huang GY, Yang Z, Zhang YF: Heat conduction of air in nano spacing.

    Nanoscale Res Lett 2009, 4:850. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  22. Durkop T, Getty SA, Cobas E, Fuhrer MS: Extraordinary mobility in semiconducting carbon nanotubes.

    Nano Lett 2004, 4:35. Publisher Full Text OpenURL

  23. Bolotina KI, Sikesb KJ, Jiang Z, Klima M, Fudenberg G, Hone J, Kim P, Stormer HL: Ultrahigh electron mobility in suspended grapheme.

    Solid State Commun 2008, 146:351. Publisher Full Text OpenURL