First principles simulation studies using the density functional theory have been performed on (9, 0) Zigzag Singlewalled Carbon Nanotube (SWCNT) to investigate its electronic, optical and thermodynamic properties using CASTEP (Cambridge Sequential Total Energy Package) and DFTB (Density Functional based Tight Binding) modules of the Material Studio Software version 7.0. Various functionals and sub-functionals available in the CASTEP Module (using Pulay Density Mixing treatment of electrons) and various eigen-solvers and smearing schemes available in the DFTB module (using smart algorithm) have been tried out to chalk out the electronic structure. The analytically deduced values of the band gap obtained were compared with the experimentally determined value reported in the literature. By comparison, combination of Anderson smearing scheme and standard diaogonalizer produced best results in DFTB module while in the CASTEP module, GGA (General Gradient approximation) functional with RPBE (Revised-perdew-Burke-Ernzerh) as Sub-functional was found to be the most consistent. These optimized parameters were then used to determine various electronic, optical and thermodynamic properties of (9, 0) Singlewalled Nanotube. (9, 0) Singlewalled Nanotube, which is extensively being used for sensing NH3, CH4 & NO2, has been picked up in particular as it is reported to exhibit a finite energy band gap in contrast to its expected metallic nature. The study is of utmost significance as it not only probes and validates the simulation route for predicting suitable properties of nanomaterials but also throws light on the comparative efficacy of the different approximation and rationalization quantum mechanical techniques used in simulation studies.

1. Iijima S. Helical microtubules of graphitic carbon. Nature 1991; 354: 56–58.

2. Iijima S, Ichihashi T. Single-shell carbon nanotubes of 1-nm diameter. Nature 1993; 363: 603–605.

3. Bethune DS, Johnson RD, Salem JR, et al. Atoms in carbon cages: The structure and properties of endohedral fullerenes.Nature 1993; 366: 123–128.

4. Wilson WL, Seabron E, Maclaren S, et al. (Invited) Scan-probe microwave reflectance of horizontally aligned arrays of Single-Walled Carbon Nanotubes: Nanoscale imaging of SWNT electrical properties in the Quantum Regime. ECS Meeting Abstracts 2015; 6: 769–769.

5. Park S, Nam JH, Koo JH, et al. Enhancement of ambipolar characteristics in single-walled carbon nanotubes using C 60 and fabrication of logic gates. Applied Physics Letters 2015;106: 103501.

6. Verma P, Saini P, Malik RS, et al. Excellent electromagnetic interference shielding and mechanical properties of high loading carbon-nanotubes/polymer composites designed using melt recirculation equipped twin-screw extruder. Carbon 2015; 89: 308–317.

7. Hartmann S, Sturm H, Blaudeck T, et al. Experimental and computational studies on the role of surface functional groups in the mechanical behavior of interfaces between single-walled carbon nanotubes and metals. Journal of Materials Science 2015; 50: 1–17.

8. Titova LV, Pint CL, Zhang Q, et al. Generation of terahertz radiation by optical excitation of aligned carbon nanotubes. Nano letters 2015; 15: 3267–3272.

9. Battie Y, Broch L, Naciri AE, et al. Diameter dependence of the optoelectronic properties of single walled carbon nanotubes determined by ellipsometry. Carbon 2015; 83: 32–39.

10. Sharkey JJ, Stranks SD, Huang J, et al. Engineering nanostructures by binding single molecules to single-walled carbon nanotubes. ACS nano 2014; 8: 12748–12754.

11. Vosgueritchian M, Fang Y, Park S, et al. High-yield sorting of small-diameter carbon nanotubes for solar cells and transistors. ACS Nano 2014; 8(3): 2609–2617.

12. Bauschlicher Jr CW, Ricca A. Binding of NH3 to graphite and to a (9, 0) carbon nanotube. Physical Review B 2004; 70(11): 115409.

13. Ricca A, Bauschlicher CW. The physisorption of CH4 on graphite and on a (9, 0) carbon nanotube. Chemical physics 2006; 324(2): 455–458.

14. Ricca A, Bauschlicher CW. The adsorption of NO2 on (9, 0) and (10, 0) carbon nanotubes. Chemical physics 2006; 323(2): 511–518.

15. Zhang X, Zhao J, Tange M, et al. Sorting semiconducting single walled carbon nanotubes by poly (9, 9-dioctylfluorene) derivatives and application for ammonia gas sensing. Carbon 2015; 94: 903–910.

16. Tamburri E, Angjellari M, Tomellini M, et al. Electrochemical growth of nickel nanoparticles on carbon nanotubes fibers: Kinetic modeling and implications for an easy to handle platform for gas sensing device. Electrochimica Acta 2015; 157: 115–124.

17. Olney D, Fuller L, Santhanam KSV. Addendum to “A greenhouse gas silicon microchip sensor using a conducting composite with single walled carbon nanotubes”. Sensors & Actuators B: Chemical 2014; 203: 942.

18. Dhall S, Jaggi N, Nathawat R. Functionalized multiwalled carbon nanotubes based hydrogen gas sensor. Sensors and Actuators A: Physical 2013; 201: 321–327.

19. Dhall S, Sood K, Jaggi N. A hydrogen gas sensor using a Pt-sputtered MWCNTs/ZnO nanostructure. Measurement Science and Technology 2014; 25: 085103.

20. Cakmak E, Fang X, Yildiz O, et al. Carbon nanotube sheet electrodes for anisotropic actuation of dielectric elastomers. Carbon 2015; 89: 113–120.

21. Park S, Park J, Jo I, et al. In situ hybridization of carbon nanotubes with bacterial cellulose for three-dimensional hybrid bioscaffolds. Biomaterials 2015; 58: 93–102.

22. Mao H, Kawazoe N, Chen G. Cell response to single-walled carbon nanotubes in hybrid porous collagen sponges. Colloids and Surfaces B: Biointerfaces 2015; 126: 63–69.

23. Sung SJ, Kim T, Yang SJ, et al. New insights into the oxidation of single-walled carbon nanotubes for the fabrication of transparent conductive films. Carbon 2015; 81: 525–534.

24. Zhang Z, Geng H, Wang Y, et al. Temperature and voltage dependent current–voltage behavior of single-walled carbon nanotube transparent conducting films. Applied Surface Science 2015; 355: 1201–1205.

25. Raïssi M, Vignau L, Cloutet E, et al. Soluble carbon nanotubes/phthalocyanines transparent electrode and interconnection layers for flexible inverted polymer tandem solar cells. Organic Electronics 2015; 21: 86–91.

26. Rowell MW, Topinka MA, McGehee MD, et al. Organic solar cells with carbon nanotube network electrodes. Applied Physics Letters 2006; 88: 233506.

27. Kahn BE. Patterning Processes for Flexible Electronics. Proceedings of the IEEE 2015; 103: 497–517.

28. Engel M, Steiner M, Seo JWT, et al. Hot spot dynamics in carbon nanotube array devices. Nano letters 2015; 15(3): 2127–2131.

29. Bottacchi F, Petti L, Späth F, et al. Polymer-sorted (6, 5) single-walled carbon nanotubes for solu-tion-processed low-voltage flexible microelectronics. Applied Physics Letters 2015; 106(19): 193302.

30. Javey A, Guo J, Wang Q, et al. Ballistic carbon nanotube field-effect transistors. Nature 2003; 424(6949): 654–657.

31. Sazonova V, Yaish Y, Üstünel H, et al. A tunable carbon nanotube electromechanical oscillator. Nature 2004; 431(7006): 284–287.

32. Xu X, Zhai J, Chen Y, et al. Well-aligned single-walled carbon nanotubes for optical pulse generation and laser operation states manipulation. Carbon 2015; 95: 84–90.

33. Irita M, Homma Y. Field emission from diameter‐defined single‐walled carbon nanotubes. Surface and Interface Analysis 2014; 46(12-13): 1282–1285.

34. Payne MC, Teter MP, Allan DC, et al. Iterative minimization techniques for ab initio total-energy calculations: Molecular-dynamics and conjugate gradients. Reviews of Modern Physics 1992; 64: 1045–1097.

35. Hohenberg P, Kohn W. Inhomogeneous electron gas. Physics Review 1964; 136: B864–B871.

36. Kohn W, Sham LJ. Self-consistent equations including exchange and correlation effects. Physical Review Journals archive 1965; 140, A1133–A1138.

37. Perdew JP, Zunger A. Self-interaction correction to density-functional approximations for many-electron systems. Physics Review B 1981; 23: 5048–5079.

38. Ceperley DM, Alder BJ. Ground state of the electron gas by a stochastic method. Physical Review Letters 1980; 45: 566–569.

39. Gunnarsson O, Lundqvist BI. Exchange and correlation in atoms, molecules, and solids by the spin-density-functional formalism. Physics Review B 1976; 13: 4274–4298.

40. Perdew JP, Wang Y. Accurate and simple analytic representation of the electron-gas correlation energy. Physics Review B 1992; 45: 13244–13249.

41. Perdew JP, Burke K, Ernzerhof M. Generalized gradient approximation made simple. Physical Review Letters 1995; 77: 3865–3868.

42. Tao J, Perdew JP, Staroverov VN, et al. Climbing the density functional ladder: Non-empirical meta-generalized gradient approximation designed for molecules and solids. Physical Review Let-ters 2003; 91: 146401.

43. Martin R. Electronic structure: Basic theory and practical methods. Cambridge, UK: Cambridge University Press; 2004.

44. Clark SJ, Segall MD, Pickard CJ, et al. First principles methods using CASTEP. Zeitschrift für Kristallographie—Crystalline Materials 2005; 220(5-6): 567–570.

45. Blum V, Gehrke R, Hanke F, et al. Ab initio molecular simulations with numeric atom-centered orbitals. Computer Physics Communications 2009; 180: 2175–2196.

46. Kresse G, Furthmüller J. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Physics Review B 1996; 54: 11169–11186.

47. Segall M, Linda P, Probert M, et al. Materials studio CASTEP, version 2.2. Accelrys: San Diego, CA; 2002.

48. Matsuda Y, Tahir-Kheli J, Goddard III WA. Definitive band gaps for single-wall carbon nanotubes. The Journal of Physical Chemistry Letters 2010; 1(19): 2946–2950.