Browsing by Author "Simpson, Grant J."

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Autonomous Single-Molecule Manipulation Based on Reinforcement Learning
    (American Chemical Society, 2023) Ramsauer, Bernhard; Simpson, Grant J.; Cartus, Johannes J.; Jeindl, Andreas; García-López, Victor; Tour, James M.; Grill, Leonhard; Hofmann, Oliver T.; Smalley-Curl Institute; NanoCarbon Center
    Building nanostructures one-by-one requires precise control of single molecules over many manipulation steps. The ideal scenario for machine learning algorithms is complex, repetitive, and time-consuming. Here, we show a reinforcement learning algorithm that learns how to control a single dipolar molecule in the electric field of a scanning tunneling microscope. Using about 2250 iterations to train, the algorithm learned to manipulate the molecule toward specific positions on the surface. Simultaneously, it generates physical insights into the movement as well as orientation of the molecule, based on the position where the electric field is applied relative to the molecule. This reveals that molecular movement is strongly inhibited in some directions, and the torque is not symmetric around the dipole moment.
  • Thumbnail Image
    Item
    Directing and Understanding the Translation of a Single Molecule Dipole
    (Amerian Chemical Society, 2023) Simpson, Grant J.; García-López, Víctor; Boese, A. Daniel; Tour, James M.; Grill, Leonhard; Smalley-Curl Institute; NanoCarbon Center
    Understanding the directed motion of a single molecule on surfaces is not only important in the well-established field of heterogeneous catalysis but also for the design of artificial nanoarchitectures and molecular machines. Here, we report how the tip of a scanning tunneling microscope (STM) can be used to control the translation direction of a single polar molecule. Through the interaction of the molecular dipole with the electric field of the STM junction, it was found that both translations and rotations of the molecule occur. By considering the location of the tip with respect to the axis of the dipole moment, we can deduce the order in which rotation and translation take place. While the molecule–tip interaction dominates, computational results suggest that the translation is influenced by the surface direction along which the motion takes place.
  • Thumbnail Image
    Item
    How to control single-molecule rotation
    (Springer Nature, 2019) Simpson, Grant J.; García-López, Víctor; Daniel Boese, A.; Tour, James M.; Grill, Leonhard
    The orientation of molecules is crucial in many chemical processes. Here, we report how single dipolar molecules can be oriented with maximum precision using the electric field of a scanning tunneling microscope. Rotation is found to occur around a fixed pivot point that is caused by the specific interaction of an oxygen atom in the molecule with the Ag(111) surface. Both directions of rotation are realized at will with 100% directionality. Consequently, the internal dipole moment of an individual molecule can be spatially mapped via its behavior in an applied electric field. The importance of the oxygen-surface interaction is demonstrated by the addition of a silver atom between a single molecule and the surface and the consequent loss of the pivot point.