No one will be able to see a mathematical structure as a perfect space. And now scientists using supercomputer simulations and atomic-resoul microscopes have shown (See Electron Orbital Signture) the signature of electron orbitals, which are defined by the mathematical formulation of quantum-mechanical mathematical equations that predict the location of the electron of an atom the farthest.
Scientists from UT Austin, Princeton University and ExxonMobil have discovered electron orbital signatures of two different transition metals, iron (Fe) and cobalt (Co) in fallen phthalocyanines. These signatures are evident in the energies expected from atomic force microscopes, which often reflect the underlying orbitals and can be rotated.
Their study was published as an editors’ presentation in the journal Nature Communications (“Observation of single-atom electron orbital signatures in metal-phthalocyanines using atomic force microscopy”).
“Our collaborators at Princeton University found that although Fe and Co are adjacent atoms in the periodic table, showing similarities, the corresponding energy patterns in their measured images show differences variety of experiments,” said author James R. Chelikowsky, WA \”Tex” Moncrief, Jr. Professor of mathematics and professor in the departments of physics, chemical engineering, and chemistry at UT Austin’s College of Natural Sciences.
Chelikowsky is also the director of the Center for Computational Materials at the Oden Institute for Computational Engineering and Sciences.
Without an analytical method, the Princeton scientists could not determine the source of the friction they observed using non-contact atomic force microscopy (HR-AFM) and spectroscopy that measures molecular forces of the order of piconewtons (pN), a trillion newtons.
“When we first looked at the experimental images, our first reaction was to wonder how the experiment could capture such subtle differences. These are small forces,” added Chelikowsky.
“By using techniques such as atomic microscopy, we can better understand how atoms and molecules behave, and maybe even how to create and create new things that have certain properties. This is especially important in areas such as materials science, nanotechnology and catalysis,” said Chelikowsky.
The calculation of the required electronic structure is based on Density Functional Theory (DFT), which starts from the equations of quantum systems and serves as a useful method for predicting the behavior of matter.
“Our main contribution is that we have confirmed from our existing DFT calculations that the observed experimental differences arise from different electron configurations in the 3d electrons of Fe and Co near the Fermi level, the lowest energy state . is higher than the electron. can enter the atom,” said the first author of the paper Dingxin Fan, a former graduate student working with Chelikowsky. Fan is currently a postdoctoral researcher at the Princeton Materials Institute.
The DFT calculation includes a copper substrate for Fe and Co atoms, adding a few hundred atoms to the mix calls for intensive calculations, which they have enabled on the Stampede2 supercomputer at the Texas Advanced Computing Center (TACC), which approved by National Science Foundation.
“In the case of our model, at high altitudes we moved the carbon monoxide tip of the AFM over the sample and calculated the number of forces at each grid point in the distance,” said Fan. . “It involved hundreds of different calculations. TACC’s Stampede2 software package helped us analyze the data more easily. For example, the Visual Molecular Dynamics software facilitates the analysis of our mathematical results.
“Stampede2 has provided excellent computational and security capabilities to support the various research projects we have,” added Chelikowsky.
By showing that the orbital signature of electrons is visible using AFM, the scientists say that this new knowledge can quickly extend the application of AFM in different areas.
In addition, their study used an inactive molecular probe to approach another molecule and accurately measure the interaction between the two molecules. This allowed the scientific team to study the chemical reactions on the surface.
For example, suppose that a catalyst can speed up a chemical reaction, but the molecular site responsible for catalysis is unknown. In this case, it is possible to use AFM tips prepared with molecular reagents to measure interactions with different sites, ultimately identifying the active site(s) of the chemical.
In addition, since orbital level information can be obtained, scientists can better understand what will happen when chemical reactions occur. As a result, other scientists can create better things based on this information.
Chelikowsky says: “In many ways, supercomputers allow us to control how atoms interact without going into a laboratory. Such work can lead to the discovery of new things without a rigorous “trial and error” process.
Source: The University of Texas at Austin
