5 research outputs found
Cavity-free continuum solvation: implementation and parametrization in a multiwavelet framework
We present a multiwavelet-based implementation of a quantum/classical
polarizable continuum model. The solvent model uses a diffuse solute-solvent
boundary and a position-dependent permittivity, lifting the sharp-boundary
assumption underlying many existing continuum solvation models. We are able to
include both surface and volume polarization effects in the quantum/classical
coupling, with guaranteed precision, due to the adaptive refinement strategies
of our multiwavelet implementation. The model can account for complex solvent
environments and does not need a posteriori corrections for volume polarization
effects. We validate our results against a sharp-boundary continuum model and
find very good correlation of the polarization energies computed for the
Minnesota solvation database
4-component Relativistic Calculations in a Multiwavelet Basis with Improved Convergence
The many-body wave function of an -electron system within a relativistic
framework can be described by the Dirac equation. Unfortunately, the Dirac
operator is unbounded and in case we would describe anions
we will observe the variational collapse of wavefunction of electron.
Thus, it is necessary to avoid it and an alternative approach is based on
applying the square of the Dirac operator . This
approach is especially suitable for a multiwavelet framework: its
implementation in an integral equation form is readily available and the
completeness of the multiwavelet basis guarantees that the matrix
representation of in the occupied space is identical
to the square of the matrix representation of . This
equivalence is not valid in a finite basis set. The use of the
operator within a multiwavelet framework is able to
achieve higher precision compared to the , consistent with
the quadratic nature of the error estimates in a variational framework.Comment: Submitted to Theoretical Chemistry Account
VAMPyR—A high-level Python library for mathematical operations in a multiwavelet representation
Wavelets and multiwavelets have lately been adopted in quantum chemistry to overcome challenges presented by the two main families of
basis sets: Gaussian atomic orbitals and plane waves. In addition to their numerical advantages (high precision, locality, fast algorithms for
operator application, linear scaling with respect to system size, to mention a few), they provide a framework that narrows the gap between
the theoretical formalism of the fundamental equations and the practical implementation in a working code. This realization led us to the
development of the Python library called VAMPyR (Very Accurate Multiresolution Python Routines). VAMPyR encodes the binding to a C++
library for multiwavelet calculations (algebra and integral and differential operator application) and exposes the required functionality to
write a simple Python code to solve, among others, the Hartree–Fock equations, the generalized Poisson equation, the Dirac equation, and
the time-dependent Schrödinger equation up to any predefined precision. In this study, we will outline the main features of multiresolution
analysis using multiwavelets and we will describe the design of the code. A few illustrative examples will show the code capabilities and its
interoperability with other software platforms
MRChem Multiresolution Analysis Code for Molecular Electronic Structure Calculations: Performance and Scaling Properties
MRChem is a code for molecular electronic structure calculations,
based on a multiwavelet adaptive basis representation. We provide
a description of our implementation strategy and several benchmark
calculations. Systems comprising more than a thousand orbitals are
investigated at the Hartree–Fock level of theory, with an emphasis
on scaling properties. With our design, terms that formally scale
quadratically with the system size in effect have a better scaling
because of the implicit screening introduced by the inherent adaptivity
of the method: all operations are performed to the requested precision,
which serves the dual purpose of minimizing the computational cost
and controlling the final error precisely. Comparisons with traditional
Gaussian-type orbitals-based software show that MRChem can be competitive
with respect to performance