4 research outputs found
Implementation and Application of the Frozen Density Embedding Theory with the Algebraic Diagrammatic Construction Scheme for the Polarization Propagator up to Third Order
Implementation,
benchmarking, and representative applications of
the new FDE-ADC(3) method for describing environmental effects on
excited states as a combination of frozen density embedding (FDE)
and the algebraic-diagrammatic construction scheme for the polarization
propagator of third order (ADC(3)) are presented. Results of FDE-ADC(3)
calculations are validated with respect to supersystem calculations
on test systems with varying moleculeâenvironment interaction
strengths from dispersion up to multiple hydrogen bonds. The overall
deviation compared to the supersystem calculations is as small as
0.029 eV for excitation energies, which is even smaller than the intrinsic
error of ADC(3). The dependence of the accuracy on the choice of method
and functional for the calculation of the environment and the nonelectrostatic
part of the systemâenvironment interaction is evaluated. In
three representative examples, the FDE-ADC method is applied to investigate
larger systems and to analyze excited state properties using visualization
of embedded densities and orbitals
Utilizing the 8âMethoxycyclooct-4-en-1-ide Unit As a Hydrogen Atom Acceptor en Route to âMetalâBorane Pincersâ
The synthesis and characterization of palladium and platinum
complexes
containing the neutral ligand HBÂ(mp)<sub>2</sub> (where mp = 2-mercaptopyridyl)
are presented. Addition of 2 equiv of NaÂ[H<sub>2</sub>BÂ(mp)<sub>2</sub>] to [MÂ(Cl)Â(COE<sup>OMe</sup>)]<sub>2</sub> (where M = Pt, Pd; COE<sup>OMe</sup> = 8-methoxycyclooct-4-en-1-ide) in the presence of 2 equiv
of PPh<sub>3</sub> leads to the formation of the metalâborane
pincer complexes [PtÂ{Îș<sup>3</sup><i>SBS</i>-HBÂ(mp)<sub>2</sub>}Â(PPh<sub>3</sub>)] and [PdÂ{Îș<sup>3</sup><i>SBS</i>-HBÂ(mp)<sub>2</sub>}Â(PPh<sub>3</sub>)]. In these reactions, a hydrogen
migration reaction occurs from the borohydride ligand to the metal
center, eventually leading to the elimination of the COE<sup>OMe</sup> unit from the metal center. X-ray crystallographic characterization
of the two isostructural complexes reveals a rare <i>mer</i>-Îș<sup>3</sup><i>S</i>,<i>B</i>,<i>S</i> coordination mode with short platinumâ and palladiumâboron
distances: 2.098(4) and 2.091(3) Ă
, respectively (the shorter
distances of two independent complexes in the unit cells of both structures).
The complexes [PdÂ{Îș<sup>3</sup><i>S</i>,<i>B</i>,<i>S</i>-HBÂ(mp)<sub>2</sub>}Â(PPh<sub>3</sub>)] and [PtÂ{Îș<sup>3</sup><i>S</i>,<i>B</i>,<i>S</i>-HBÂ(mp)<sub>2</sub>}Â(PPh<sub>3</sub>)] are the first examples of metalâborane
complexes featuring a pincer-type coordination where one hydrogen
substituent remains at the boron center
Benchmark of Excitation Energy Shifts from Frozen-Density Embedding Theory: Introduction of a Density-Overlap-Based Applicability Threshold
We
present a thorough investigation of the errors in results obtained
with the combination of frozen-density embedding theory and the algebraic
diagrammatic construction scheme for the polarization propagator of
second order (FDE-ADC(2)). The study was carried out on a set of 52
intermolecular complexes with varying interaction strength, each consisting
of a chromophore of fundamental interest and a few small molecules
in its environment. The errors emerging in frozen-density embedding
theory-based methods originate from (a) the solver of the quantum
many-body problem used to obtain the embedded wave function (Κ<sub>A</sub><sup>emb</sup>), (b) the approximation
for the explicit density functional for the embedding potential, and
(c) the choice of the density representing the environment (Ï<sub>B</sub>(<i>râ</i>)). The present work provides a
comprehensive analysis of the errors in the excitation energies based
on the last two factors. Furthermore, a density-overlap-based parameter
is proposed to be used as an a priori criterion of applicability
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