Why do carbon nanotubes grow chiral?

Why do carbon nanotubes grow chiral? Evgeni S. Penev, Vasilii I. Artykhov, Boris I. Yakobson Departent of Materials Science and NanoEngineering, Rice University

E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

Challenges & big questions Achieving chirality control in a practical way A decade of experimental advances 2013: are we approaching new level of understanding ∴ control. . . ? Can theory help understanding observed preferences? Experiment

Theory

? He et al., Sci. Rep. 3, 1460 (2013) E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

Improving selectivity. . . : an eclectic view

Selection of ∼ 20 experiments Time-span: ' 2003–2013 (n, n − 1) predominant Near-armchair preference “veiled in mystery” He et al., Sci. Rep. 3, 1460 (2013)

Do we have a proper language to articulate, rationalize such a “mystery”? E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

Selectivity as a “life-time” integral Abundance of a nanotube type (n, m): a hypothesis (heuristic formulation) Pn,m ∼

Z

nucl growth pn,m (t)vn,m (t). . . dt

Penev, Artyukhov, Ding, Yakobson, Adv. Mater. 24, 4956 (2012)

(n, m) −→ (diameter d,chiral angle χ) P(χ) – strongly nonlinear, but why peaked at near-armchair?

(n, n)

(n, n − 1)

E. Penev http://penev.objectis.net

(n, m)

APS MAR14 Meeting, March 6, 2014

Prerequisites Nucleation End-caps: no χ-bias

d HnmL

1.0

0.8 0.6

CNT|catalyst interface: γ = γ(χ)

Growth Steady-state: K (χ) ∼ χ

WHeVL

10

8

6 ZZ Χ

AC

Penev, Artykhov, Yakobson, ACS Nano 8, 1899 (2014)

Next talk: S37.00008

Liu, Dobrinsky, Yakobson, Phys. Rev. Lett. 105, 235502 (2010) Ding, Harutyunyan, Yakobson, PNAS 106, 2506 (2009)

E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

nucl growth , vn,m from atomistic computations pn,m Protocol: DFT, ReaxFF; catalyst: Ni(111), Nin Interface thermodynamic: regular, “Klein”-edges → pn,m

Material accretion: C, C2 attachment → vn,m

Pathways . . . . . . . . . . . . . . . . . . . . . . . . E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

Resultant CNT type distributions Pn,m Selected diameters: d ' 0.8 nm . . . including (6,5) d ' 1.2 nm . . . including (9,8)

Broader range of diameters d:

Theoretical hypothesis vs Experimental trends: a surprisingly good agreement E. Penev http://penev.objectis.net

APS MAR14 Meeting, March 6, 2014

Summary nucl growth An integral theoretical approach (pn,m vs. vn,m ) can explain near-armchair preference observed in experiments Simulated PL map (d ' 0.8 nm), using Lorentzian broadening: Theory Experiment

Thank you! He et al., Sci. Rep. 3, 1460 (2013)

E. Penev http://penev.objectis.net

(unpublished)

APS MAR14 Meeting, March 6, 2014