QM/MM study of the interaction between zigzag SnC nanotube and small toxic gas molecules

Adsorptions of small toxic molecules such as CO, N2, HCN, SO2, H2CO, and NH3 on a single‐walled (6,0) SnC nanotube (SnCNT) are investigated using Quantum Mechanics/Molecular Mechanics (QM/MM) methodology. The calculations are carried out at the B3LYP/6‐311++G(d,p)//LANL2DZ:UFF level of theory. The high layer of the model consists of a pyrene‐type ring on the nanotube surface as the adsorption site, where one gas molecule is allowed to interact. Conversely, for the adsorption of the two molecules, a larger site like a coronene ring is used for the high layer. Adsorption energy, Gibbs free energy change, Mulliken charge transfer, and total electron‐density maps are computed in each case. The adsorption strength of the gas molecule on the SnCNT surface is also analyzed from the density of states projected to different atoms (PDOS) of the nanotube–adsorbate complexes. The adsorptions of CO and N2 on the (6,0) SnCNT surface require to cross potential barriers, and the corresponding transition structures are identified by ONIOM‐IRC calculations. For the remaining four molecules, the processes of adsorption are predicted to be barrier‐less. The calculations for the adsorption of H2CO on (5,0) and (7,0) SnCNT surfaces are extended to study the effect of the size of the nanotube. Results for the adsorption of a single molecule on (6,0) SnCNT using B3LYP functional are compared with those obtained from a dispersion corrected functional such as M06‐2X. © 2015 Wiley Periodicals, Inc. Alternative nanotubes and nanowires have been recently investigated as replacements for carbon nanotubes as gas sensors. First‐principles calculations aid the study of single‐walled SnC nanotubes as detectors of small toxic gas molecules like CO, N2, HCN, SO2, H2CO, and NH3. The most energetically favorable structure of each adsorbed complex is reported. SO2, H2CO, and NH3 molecules show stronger affinities toward (6,0) SnCNT. The effect of dispersion corrected functionals are also modeled.