Ultra-high vacuum scanning tunneling microscopy and theoretical studies of 1-halohexane monolayers on graphite

Müller et al. 10.1073/pnas.0409576102.

Supporting Information

Files in this Data Supplement:

Fig. 7. Scanning tunneling microscopy (STM) topographs of 1-fluorohexane vs. 1-iodohexane on highly oriented pyrolytic graphite (HOPG). Constant-current STM topographs are shown for 1-fluorohexane (22.5 ´ 22.5 nm, V_bias = 1.9 V, I_setp = 100 pA) (a) and 1-iodohexane (150 ´ 150 nm, V_bias = 2.0 V, I_setp = 85 pA) (b). In the case of 1-fluorohexane, the lamella spacing is characterized by a substantial degree of disorder. As exemplified by the adjacent lamellae highlighted by the two yellow boxes, the alternating pattern of narrower and wider dark gaps between lamellae exhibits frequent irregularities. The solid blue bar in each box indicates two 1-fluorohexane molecules pointed head-to-head. Note that following the dashed yellow line up to the top yellow box shows that the molecules have now flipped, the solid blue bar indicates the position of two head-to-head molecules, and the dashed bar shows where the pair used to be (see bottom yellow box). In contrast, monolayers of 1-iodohexane exhibit single adsorbate domains with few defects over length scales of micrometers.

Fig. 8. Fifty 1-bromohexane molecules after 50 ps of constant number/volume/temperature (NVT) molecular dynamics at different temperatures. The adsorbate islands resulting from the energy minimization displayed in Fig. 4a were subjected to 50 ps of constant NVT molecular dynamics without periodic boundary conditions. Structures were obtained at 50 K (a), 75 K (b), 100 K (c), and 150 K (d), respectively.

Fig. 9. Simulation of 50 1-fluorohexane molecules on graphite at 50 K followed by minimization, without image charge effects included. Results are shown for a molecular dynamics simulation of 50 1-fluorohexane molecules at 50 K for 50 ps. The starting configuration was identical to that used previously (Fig. 6b); however, for the molecular dynamics simulation, the image charge term was not included in the potential. None of the long-range structure is maintained. The size of this image is » 270 ´ 200 Å, expanded from an initial relatively tight packed structure of dimensions <100 ´ 20 Å.

• Early Edition
• Archives
• Online Submission

• Feature Articles

  (Expanded research articles of exceptional breadth)

• Commentaries

  (Expert commentary on leading research)

• Letters

  (Online-only letters to the editor)

• Inaugural Articles

  (Articles by recently elected NAS members)

• PNAS Profiles

  (Biographical profiles of Academy members)

• Sustainability Science

  (Interactions of human and environmental systems)

• Collected Papers

  (Editorials, Perspectives, Reviews, Colloquia, etc.)

• Special Features

  (Solicited articles on exceptional research topics)

• Sackler Colloquia

  (Scientific reports held under NAS auspices)

• Podcasts

  Brief podcasts with leading scientists