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@olivieroandreussi olivieroandreussi released this Apr 18, 2019 · 118 commits to master since this release

First official release of the Environ library for multiscale environment effects in condensed-matter simulations. Environ 1.0 is coupled with the Quantum Espresso package (www.quantum-espresso.org).
The new features of Environ-1.0 are the following:

  • Preconditioned conjugate gradient solvers for the generalized Poisson equation, needed in dielectric embedding environments.
  • Extension to solve linearized (possibly size-modified) Poisson-Boltzmann problems, needed in modeling dilute electrolyte embedding environments.
  • Non-linear solvent-aware definition of the continuum interface, to avoid artifacts in the definition of the boundary in complex systems, such as unphysical pockets of continuum embedding environments that are smaller than the solvent molecular radius.
  • A full set of tests to check consistency of compilation and implementation.

The previous functionalities of Environ, available to all the supported distributions of Quantum Espresso, are the following:

  • Continuum dielectric solvation model, defined self-consistently on the electronic density of the system.
  • External pressure model, defined in terms of the quantum-volume of the system.
  • External surface tension model, defined in terms of the quantum-surface of the system.
  • Point-counter-charge correction schemes to remove periodic boundary conditions artifacts in isolated (0D) and slab (2D) systems.
  • Modifications of Martyna-Tuckermann PBCs correction schemes to account for the presence of a continuum dielectric embedding.
  • Fully tested and easier to use external fixed charge densities of arbitrary shape and dimensionality.
  • External user-defined dielectric regions of arbitrary shape and dimensionality, to simulate the effect of complex environment such as interfaces, substrates, nanoparticles, etc.
  • Restart, with the possibility to include environment effects from the initialization step, providing a substantial speedup for geometry optimization calculations.

The above functionalities are coupled with the following types of calculations:

  • Possibility to perform single point calculations, geometry optimizations, and Born-Oppenheimer molecular dynamics simulations, through the PW code of the Quantum Espresso package.
  • Possibility to perform transition state calculations via the nudged elastic band method, through the NEB code of the Quantum Espresso package.
  • Possibility to perform the calculation of optical spectra via time-dependent density functional perturbation theory, through the TDDFpT code (only for the continuum dielectric contribution).
  • Only starting from QE-5.3.0, Environ-0.2 is coupled with the CP code of the Quantum Espresso package, to perform Car-Parrinello and damped molecular dynamics simulations.

All the above simulations are compatible with the main features of Quantum Espresso, namely pseudo-potentials-based plane-wave periodic-boundary-conditions simulations at the density functional theory level, with k-point integration. In particular the following features are all compatible with Environ (a more comprehensive list of the capabilities of Quantum Espresso can be found in the project documentation):

  • Norm-conserving, ultrasoft and projector-augmented wave (PAW) pseudopotentials.
  • Local density approximation (LDA) functionals, Generalized Gradient approximation (GGA) functionals, hybrid functionals, van der Waals (vdW) nonlocal density functionals.
  • Hubbard U.
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