text: Computational Design of Chemical Nanosensors: Metal Doped Carbon Nanotubes 
  
  J. M. Garc´ıa-Lastra1,2,∗ D. J. Mowbray1,2, K. S. Thygesen2, A. Rubio1,3, and K. W. Jacobsen2 
  1Nano-Bio Spectroscopy group and ETSF Scientiﬁc Development Centre, 
  Dpto. F´ısica de Materiales, Universidad del Pa´ıs Vasco, 
  Centro de F´ısica de Materiales CSIC-UPV/EHU- MPC and DIPC, Av. Tolosa 72, E-20018 San Sebasti´an, Spain 
  2Center for Atomic-scale Materials Design, Department of Physics, 
  Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark 
  3Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin, Germany 
  
  We use computational screening to systematically investigate the use of transition metal doped carbon nan- 
  otubes for chemical gas sensing. For a set of relevant target molecules (CO, NH3, H2S) and the main components 
  of air (N2, O2, H2O), we calculate the binding energy and change in conductance upon adsorption on a metal 
  atom occupying a vacancy of a (6,6) carbon nanotube. Based on these descriptors, we identify the most promis- 
  ing dopant candidates for detection of a given target molecule. From the fractional coverage of the metal sites 
  in thermal equilibrium with air, we estimate the change in the nanotube resistance per doping site as a function 
  of the target molecule concentration assuming charge transport in the diffusive regime. Our analysis points to 
  Ni-doped nanotubes as candidates for CO sensors working under typical atmospheric conditions. 