Visualizing the Microscopic World

VMD Store-A VMD Plugin to Browse, Discover, and Install VMD Extensions

Herein we present the VMD Store, an open-source VMD plugin that simplifies the way that users browse, discover, install, update, and uninstall extensions for the Visual Molecular Dynamics (VMD) software. The VMD Store obtains data about all the indexed VMD extensions hosted on GitHub and presents a one-click mechanism to install and configure VMD extensions. This plugin arises in an attempt to aggregate all VMD extensions into a single platform. The VMD Store is available, free of charge, for Windows, macOS, and Linux at https://biosim.pt/software/ and requires VMD 1.9.3 (or later).

Visualizing atomic sizes and molecular shapes with the classical turning surface of the Kohn-Sham potential

The Kohn-Sham potential [Formula: see text] is the effective multiplicative operator in a noninteracting Schrödinger equation that reproduces the ground-state density of a real (interacting) system. The sizes and shapes of atoms, molecules, and solids can be defined in terms of Kohn-Sham potentials in a nonarbitrary way that accords with chemical intuition and can be implemented efficiently, permitting a natural pictorial representation for chemistry and condensed-matter physics. Let [Formula: see text] be the maximum occupied orbital energy of the noninteracting electrons. Then the equation [Formula: see text] defines the surface at which classical electrons with energy [Formula: see text] would be turned back and thus determines the surface of any electronic object. Atomic and ionic radii defined in this manner agree well with empirical estimates, show regular chemical trends, and allow one to identify the type of chemical bonding between two given atoms by comparing the actual internuclear distance to the sum of atomic radii. The molecular surfaces can be fused (for a covalent bond), seamed (ionic bond), necked (hydrogen bond), or divided (van der Waals bond). This contribution extends the pioneering work of Z.-Z. Yang et al. [Yang ZZ, Davidson ER (1997) Int J Quantum Chem 62:47-53; Zhao DX, et al. (2018) Mol Phys 116:969-977] by our consideration of the Kohn-Sham potential, protomolecules, doubly negative atomic ions, a bond-type parameter, seamed and necked molecular surfaces, and a more extensive table of atomic and ionic radii that are fully consistent with expected periodic trends.