The goal of quantum-chemical calculations is the simulation of materials and molecules. In density-functional theory (DFT) the first step along this line is obtaining the electron density minimising an energy functional. However, since energies and the density are usually not very tractable quantities in an experimental setup, comparison to experiment …

read more# Surrogate models for quantum spin systems based on reduced order modeling

The simulation of quantum spin models is an actively researched field. Albeit rather basic these many-body systems are inherently strongly correlated and as such feature a rich variety of phaenomena including involved patterns of ordering / discordering, topological order or varieties of phase changes. Furthermore these models often provide a good …

read more# Quantum Chemistry Common Driver and Databases (QCDB) and Quantum Chemistry Engine (QCEngine): Automation and Interoperability among Computational Chemistry Programs

As part of my previous work on the adcc code for computational spectroscopy based on the algebraic-diagrammatic construction (ADC), we also integrated the package with QCEngine. This package aims at integrating different quantum-chemistry codes under a common interface for end users, which is an effort I fully support. Recently the …

read more# A robust and efficient line search for self-consistent field iterations

In an ongoing effort with Antoine Levitt our aim is to develop reliable density-functional theory (DFT) methods for computational materials design. Recently we looked into a strategy to automatically select the damping parameter for the self-consistent field iterations (SCF). Our

read more**adaptive damping**approach is based on a theoretically sound quadratic …# Q-Chem 5 paper

About two years ago I integrated my open-source ctx library into the Q-Chem quantum-chemistry software suite. Quickly

read more`ctx`

became part of the core stack for managing computational results inside Q-Chem. In particular inside the`ccman`

and`adcman`

modules, which are responsible for most of the coupled-cluster and algebraic-diagrammatic construction methods …# DFTK: A Julian approach for simulating electrons in solids

Following my talk at Juliacon about our DFTK code last year (slides, recording, blog article), we have now published an extended abstract in the JuliaCon proceedings, which you can find below. The JuliaCon proceedings use the same open journals software stack to manage their publication infrastructure as the Journal of …

read more# Gator: a Python-driven program for spectroscopy simulations

A bit over a year ago we published our adcc code. In this work the aim was to develop a toolkit for computational spectroscopy methods focused on rapid development and interactive hands-on usage (see the blog article for details). Our target back then was to simplify method development involving the …

read more# Black-box inhomogeneous preconditioning for self-consistent field iterations in density-functional theory

For the past half a year or so Antoine Levitt and myself have been looking at a particular tricky busyness for solid-state density-functional theory (DFT) calculations, namely how to design efficient self-consistent field (SCF) schemes for large inhomogeneous systems. I have already previously reported on this matter in a short …

read more# Quantifying the error of the core-valence separation approximation

After only a few months of publishing our adcc paper, which introduces the novel algebraic-diagrammatic construction (ADC) code adcc, the package has already found mention in a number of related articles. One example is a manuscript on updates in the Psi4 quantum chemistry package, which features adcc as one of …

read more# A posteriori error estimation for the non-self-consistent Kohn-Sham equations

After about a year of work on the density-functional toolkit (DFTK) we finally started using the code for some new science. Given the mathematics background of the CERMICS the first two DFTK-related articles were not so much about large-scale applications, but rather deal some fundamental questions of Kohn-Sham density-functional theory …

read more# adcc: A versatile toolkit for rapid development of algebraic-diagrammatic construction methods

Over the part year or so a side project I have been working off and on has been the adcc code. This python module allows to perform excited states calculation for simulating molecular spectra based on algebraic-diagrammatic construction (ADC) methods. The speciality of the adcc code is that (a) multiple …

read more# Quantum chemistry with Coulomb Sturmians: Construction and convergence of Coulomb Sturmian basis sets at Hartree-Fock level

This week we submitted a paper related to our ongoing work regarding the use of Coulomb Sturmian basis functions in electronic structure theory. Given the recent progress, which has been made with regards to the evaluation of molecular integrals based on these exponential-type functions, molecular calculations based on Coulomb Sturmians …

read more# Embedding Combined with the Algebraic Diagrammatic Construction: Tackling Excited States in Biomolecular Systems

Yesterday the journal of chemical theory and computation accepted our manuscript titled

**Polarizable Embedding Combined with the Algebraic Diagrammatic Construction: Tackling Excited States in Biomolecular Systems**. In this work we describe the combination of the polarisable embedding (PE) scheme for including environmental effects with the algebraic-diagrammatic construction (ADC) approach.The …

read more# Towards quantum-chemical method development for arbitrary basis functions

Last week we submitted the molsturm design paper titled

**Towards quantum-chemical method development for arbitrary basis functions**. This manuscript is a condensed summary of the arguments about design and implementation of a basis-function independent self-consistent field scheme (SCF) already presented in my PhD thesis.Our approach to a basis-function-independent electronic …

read more# Publication of my PhD thesis

Finally, after quite some years of work I have successfully defended my PhD thesis with the title

**Development of a modular quantum-chemistry framework for the investigation of novel basis functions**on 22nd May. An electronic version of the text has now been published online.To make the topic of my …

read more# Oberwolfach reports: Molsturm modular electronic structure theory framework

As announced in my previous post about the Oberwolfach workshop on Mathematical Methods in Quantum Chemistry, the proceedings of each Oberwolfach workshop are published in the form of an article in the Oberwolfach reports. For this purpose each speaker is asked for an extended abstract summarising the content of his …

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