2 research outputs found
Efficient and Flexible Computation of Many-Electron Wave Function Overlaps
A new algorithm for the computation
of the overlap between many-electron
wave functions is described. This algorithm allows for the extensive
use of recurring intermediates and thus provides high computational
efficiency. Because of the general formalism employed, overlaps can
be computed for varying wave function types, molecular orbitals, basis
sets, and molecular geometries. This paves the way for efficiently
computing nonadiabatic interaction terms for dynamics simulations.
In addition, other application areas can be envisaged, such as the
comparison of wave functions constructed at different levels of theory.
Aside from explaining the algorithm and evaluating the performance,
a detailed analysis of the numerical stability of wave function overlaps
is carried out, and strategies for overcoming potential severe pitfalls
due to displaced atoms and truncated wave functions are presented
OpenMolcas: From source code to insight
In this article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already
includes a large number of new developments realized during the transition from
the commercial MOLCAS product to the open-source platform. The paper initially
describes the technical details of the new software development platform. This is followed by brief presentations of many new methods, implementations, and features
of the OpenMolcas program suite. These developments include novel wave function methods such as stochastic complete active space self-consistent field, density
matrix renormalization group (DMRG) methods, and hybrid multiconfigurational wave function and density functional theory models. Some of these implementations
include an array of additional options and functionalities. The paper proceeds and
describes developments related to explorations of potential energy surfaces. Here
we present methods for the optimization of conical intersections, the simulation of
adiabatic and nonadiabatic molecular dynamics and interfaces to tools for semiclassical and quantum mechanical nuclear dynamics. Furthermore, the article describes
features unique to simulations of spectroscopic and magnetic phenomena such as
the exact semiclassical description of the interaction between light and matter, various X-ray processes, magnetic circular dichroism and properties. Finally, the paper
describes a number of built-in and add-on features to support the OpenMolcas platform with post calculation analysis and visualization, a multiscale simulation option
using frozen-density embedding theory and new electronic and muonic basis sets