Strange things happen when a crystal is split in twoThe remarkable strength of ionic crystals is eas

Strange things happen when a crystal is split in twoThe remarkable strength of ionic crystals is easily explained at the atomic scale: Positively and negatively charged atoms sit side by side in a repeating periodic arrangement. The strong electrostatic force in between keeps them together.But what happens when the periodic pattern comes to an abrupt end? Researchers at the Vienna University of Technology have carefully broken potassium tantalate crystals in specific directions, and imaged the resulting surfaces using a state-of-the art atomic force microscope. Their data was combined with computations performed at the University of Vienna, and a series of remarkable phenomena were ultimately explained. The results were published in Science, and are potentially useful for technologies such as hydrogen production.The black and white squares on a chess board alternate along the rows and columns, and at an angle from corner to corner, they appear as black and white rows. The black and white squares in two dimensions resemble a crystal in three dimensions: “If one splits a cubic crystal along a certain direction, one can end up with only positive or only negative charges at the surface. Such a situation would be highly unstable,” explains Prof. Ulrike Diebold of he Institute of Applied Physics of the Vienna University of Technology. A stacking of purely positive and negatively charged layers would result in a potential of millions of volts across the tiny sample—scientists call this the “polar catastrophe.” To avoid this situation, the atoms must reorganize. But how?Read more. -- source link
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