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Related Concept Videos

Electronic Structure of Atoms02:28

Electronic Structure of Atoms

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An atom comprises protons and neutrons, which are contained inside the dense, central core called the nucleus, with electrons present around the nucleus. Taking into account the wave–particle duality of electrons and the uncertainty in position around the nucleus, quantum mechanics provides a more accurate model for the atomic structure. It describes atomic orbitals as the regions around the nucleus where electrons of discrete energy exist, characterized by four quantum...
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Electron configurations and orbital diagrams can be determined by applying the Aufbau principle (each added electron occupies the subshell of lowest energy available), Pauli exclusion principle (no two electrons can have the same set of four quantum numbers), and Hund’s rule of maximum multiplicity (whenever possible, electrons retain unpaired spins in degenerate orbitals).
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The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the 3s orbital, giving a 1s22s22p63s1 configuration. The electrons occupying the outermost shell orbital(s) (highest value of n) are called valence electrons, and those occupying the inner shell orbitals are called core electrons. Since the core electron shells correspond to noble gas electron configurations, we can abbreviate electron...
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Valence Bond Theory and Hybridized Orbitals02:38

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According to valence bond theory, a covalent bond results when: (1) an orbital on one atom overlaps an orbital on a second atom, and (2) the single electrons in each orbital combine to form an electron pair. The strength of a covalent bond depends on the extent of overlap of the orbitals involved. Maximum overlap is possible when the orbitals overlap on a direct line between the two nuclei.
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The Nernst Equation02:59

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Nonstandard Reaction Conditions
The interconnection between standard cell potentials and various thermodynamic parameters such as the standard free energy change ΔG° and equilibrium constant K has been previously explored. For example, a redox reaction involving zinc(II) and tin(II) ions at 1 M concentration with Eºcell = +0.291 V and ΔG° = −56.2 kJ is spontaneous.
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Electron Orbital Model01:18

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Orbitals are the areas outside of the atomic nucleus where electrons are most likely to reside. They are characterized by different energy levels, shapes, and three-dimensional orientations. The location of electrons is described most generally by a shell or principal energy level, then by a subshell within each shell, and finally, by individual orbitals found within the subshells.
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Electronic Structure Theory Calculations Using Modern Architectures: KNL vs Haswell.

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Intel Haswell processors offer faster quantum chemistry computation times than Intel Xeon Phi Knights Landing (KNL). While Haswell excels in speed, KNL shows better parallel efficiency for large-scale electronic structure calculations.

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Area of Science:

  • Computational Chemistry
  • High-Performance Computing
  • Quantum Chemistry

Background:

  • Electronic structure methods are crucial for understanding molecular behavior.
  • Evaluating computational performance across different hardware architectures is essential for optimizing scientific workflows.

Purpose of the Study:

  • To compare the performance of common electronic structure methods on Intel Haswell and Intel Xeon Phi Knights Landing (KNL) architectures.
  • To assess the time to solution and parallel efficiency of these methods on novel computing architectures.

Main Methods:

  • Benchmarking several electronic structure methods: Hartree-Fock, density functional theory, second-order perturbation theory, RI-MP2, and coupled cluster.
  • Evaluating performance on Intel Xeon Haswell and Intel Xeon Phi Knights Landing (KNL) processors.
  • Analyzing time to solution and parallel efficiency metrics.

Main Results:

  • Intel Haswell demonstrated a faster time to solution across all tested molecules and methods compared to KNL.
  • Haswell achieved an average speedup of at least 3.5x for non-threaded computations.
  • KNL exhibited superior parallel efficiency with increasing core counts.
  • For memory-intensive coupled cluster calculations on large systems, KNL's memory hierarchy and capacity offered advantages.

Conclusions:

  • Intel Haswell is generally preferred for minimizing time to solution in quantum chemistry.
  • KNL architecture offers benefits for very large, memory-intensive calculations requiring high parallel efficiency.
  • These findings highlight the potential of novel architectures to enhance quantum chemistry application efficiency.