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# CECAM flagship workshop: Error control in first-principles modelling

*(Cross-post from our report published in the Psi-k blog)*From 20th until 24th June 2022 I co-organised a workshop on the theme of Error control in first-principles modelling at the CECAM Headquarters in Lausanne (workshop website). For one week the workshop unified like-minded researchers from a range of communities, including …

read more# GdR nbody general meeting

About two weeks ago, from 10 till 13 Jan 2022 I was at the annual meeting of the French research group on many-body phaenomena, the GDR nbody. Originally scheduled to take place in person in Toulouse the Corona-related developments unfortunately caused the organisers to switch to a virtual event on …

read more# GdR REST Discussion meeting on Machine Learning

Last week on 9th and 10th December 2021 I participated in the Discussion meeting on Machine Learning been organised by the French research group REST, which is centred around theoretical spectroscopy in solids and molecules. While most participants joined remotely I was fortunately able to travel to École Polytechnique in …

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 …# JuliaCon BoF discussion session: Building a Chemistry and Materials Science Ecosystem

The second event I co-organised at this year's JuliaCon (see this article for the other) was a Birds of Feather (BoF) discussion session titled

read more*Building a Chemistry and Materials Science Ecosystem in Julia*. In this session Rachel Kurchin and I wanted to gather the various stakeholders working on Julia codes …# JuliaCon DFTK workshop: A mathematical look at electronic structure theory

From 13th July till 30th July this year's JuliaCon finally took place virtually. The first week (13th till 27th) hosted a number of three-hour live-streamed sessions of workshops, while the "regular" conference with a number of prerecorded talks started on 28th.

After my introductory talk to electronic structure theory and …

read more# Virtual materials design 2021: Black-box density-functional theory methods

On 20th and 21st July 2021 the Virtual Materials Design 2021 CECAM workshop took place virtually. I was excited about this workshop and the opportunity to get in touch with researchers working on high-throughput computational materials design. While I am not actively working in this field the special requirements of …

read more# SSD Seminar: Accelerating the discovery of tomorrow's materials by robust and error-controlled simulations

A couple of days ago, on 12th July, I was invited to present my research in the SSD Seminar Series of RWTH Aachen. Being part of the research training group on modern inverse problems as well as the School for Simulation and Data Science (SSD) the SSD seminars are interdisciplinary …

read more# Talk at many-body seminar at RWTH

On 29th June I was invited to present a short summary of my research at the seminar of the research training group Quantum Many-Body Methods at RWTH Aachen University. In the talk I give a overview over my ongoing work about reliable black-box self-consistent field schemes for high-throughput DFT calculations …

read more# Errors and uncertainty quantification in density-functional theory

On 8th June I was invited to the seminar of the Uncertainty Quantification (UQ) group of Prof. Youssef Marzouk at MIT. Youssef and I planned to have this seminar since my involvement with MIT's CESMIX project last February (see also this blog article), but it took use quite some time …

read more# Talk at MATH4UQ seminar series at RWTH

On 1st June I was invited to the MATH4UQ seminar series of the Mathematics of Uncertainty Quantification chair of Prof. Raul Tempone at RWTH Aachen University.

Over the past months I got more and more interested in mathematical methods for uncertainty quantification (UQ) as an opportunity to estimate and understand …

read more# SIAM LA: Robust and efficient accelerated methods for density-functional theory

Just one day after my talk at the SIAM Materials Science conference (blog article) I gave another talk at a SIAM meeting, this time at SIAM Linear Algebra. I was very much looking forward to participate in SIAM LA, firstly because it was the first time I attended this conference …

read more# SIAM MS: Using the density-functional toolkit to design black-box DFT methods

After being moved by one year due to the pandemic, the last two weeks (from 17th to 28th May) the SIAM materials science conference finally took place in virtual form. Unfortunately this meant that the conference was scheduled in parallel to the SIAM Linear Algebra virtual conference, where I also …

read more# Talk at Lüchow group seminar at RWTH

On 5th May I was invited to present a short summary of my research at the local theoretical chemistry research group of Prof. Dr. Arne Lüchow at RWTH Aachen. Because I wanted to give a broad overview of topics that I worked on over the past few years, I did …

read more# 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# Thoughts on initial guess methods for DFT

On Thursday I gave a brief talk in our weekly ACED differentiate group meeting about initial guess methods for starting self-consistent field calculations in methods such as density-functional theory. For preparing the talk I did a little digging into both the standard approaches used by many molecular and solid-state codes …

read more# A novel black-box preconditioning strategy for high-throughput density-functional theory

A couple of weeks ago, from 15th to 19th March, I participated in the virtual annual meeting of the German Association of Applied Mathematics and Mechanics (GAMM). For me this meeting was the first time I presented my work to an audience of applied mathematicians with a broad background and …

read more# PostDoc position at Appl. & Comput. Mathematics lab, RWTH Aachen University

This week I started my new position as a postdocotoral researcher at the Applied and Computational Mathematics (ACoM) research lab at RWTH Aachen University. The lab consists of two interdisciplinary research groups, namely the group of Prof. Dr. Manuel Torrilhon, who works on the mathematical modelling and simulation of technical …

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# CESMIX TST meeting: DFTK.jl: A multidisciplinary Julia code for density-functional theory development

These past two days I have participated in the Tri-Lab Support Team (TST) meeting of the CESMIX, the newly founded Center for the Exascale Simulation of Material Interfaces in Extreme Environments at the Massachusetts Institute of Technology. Within the next few years the idea of the CESMIX is to develop …

read more# High-throughput density-functional theory calculations: An interdisciplinary challenge

Last Thursday I was invited to give a virtual talk at the Scientific Computing Seminar of working group of Prof. Nicolas Gauger at TU Kaiserslautern. Since the research in Prof. Gauger's group mostly concerns topics which are not directly related to electronic structure theory and density-functional theory (DFT), I chose …

read more# Challenges and prospects of a posteriori error estimation in density-functional theory

Last week Wednesday I was invited to give a talk at the group seminar of the AG Christoph Jacob at TU Braunschweig, Germany. Christoph was especially interested in our recent publication on a posteriori error estimation in Kohn-Sham problems and so I decided to use the opportunity to give a …

read more# Moansi: Inhomogeneous preconditioning for density-functional theory

Last week (24th and 25th September) I attended the 4th annual meeting of the Moansi (Modelling, analysis and simulation of Molecular Systems) work group of the GAMM. I already attended the Moansi meeting last year, where I very much enjoyed both the broad range of talks at the interdisciplinary border …

read more# Faraday Discussions: New horizons in density functional theory

Following the submission of our paper on a posteriori error estimation in the Kohn-Sham equations a few months ago I was recently invited to present our work at the Faraday Discussions on New horizons in density functional theory. Being amongst speakers such as Kieron Burke, Andreas Savin or Weitao Yang …

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# DFTK: A Julian approach for simulating electrons in solids

Since last Friday I have been attending JuliaCon, the annual conference for the Julia language. Naturally given the current situation the event did not take place "on location", but was instead converted into a virtual event. Albeit the different feel compared to a real-life conference the organisers did a very …

read more# SCF preconditioning for mixed systems

Fortunately the general lockdown due to the Corona pandemic slowly starts to ease around Paris as well. While basically all seminars are only virtual it is good to see old procedures and habits to slowly return. From my end I gave the first talk after the forced break today in …

read more# First release of the density-functional toolkit (DFTK)

After we released a preliminary snapshot of DFTK last year our focus in the first half of this year was on using it for some new science. Recently, however, we got back into polishing our code base and our documentation in order to get DFTK ready for a wider audience …

read more# Recent developments in adcc

Since the publication of the adcc paper a few months back, there are a few updates to report briefly:

- adcc can now be interactively tried in the browser at try.adc-connect.org using the infrastructure from the binder project.
- Binary installation of adcc is now available via conda for Linux …

# 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# 1st GDR NBODY meeting in Lille: Applications of DFTK

Earlier this month the first annual meeting of the French working group NBODY (GDR NBODY) took place in Lille. Since the GDR NBODY is an association of interdisciplinary scientists working on

read more*N*-body problems in chemistry an physics, the about 80 participants came from a broad background ranging from quantum …# Talk in Toulouse: adcc and DFTK

A few weeks ago on 21st and 22nd November of this year Pierre-Francois Loos invited me for two days to the Laboratoire de Chimie et Physique Quantiques of the Université Paul Sabatier Toulouse. On Thursday the 21st I had the chance to present our current status in DFTK and adcc …

read more# Preview release of the density-functional toolkit (DFTK)

As part of my research stay at the Matherials team of ENPC Paris Tech and Inria I have been developing the density-functional toolkit, DFTK.jl, together with Antoine Levitt and Eric Cancès. Finally after about six months of joint effort on this Julia code, we just released a first preview …

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# JuliaParis: Electronic structure simulations using Julia

Yesterday we had the first instance of the Julia Paris Meetup. As the name suggests a couple of us Julia enthusiasts in the French capital got together for one evening of talks and chatting about everyone's favourite programming language. It was a great occasion to finally meet some people in …

read more# Interdisciplinary software for electronic structure theory: adcc and DFTK

Last week, from Wednesday to Friday, I paid the Technical University of Munich (TUM) a short visit for two great opportunities to present my work: Once in the theoretical chemistry group of Professor Wolfgang Domcke and once at the annual meeting of the modeling, analysis and simulation of molecular systems …

read more# Interdisciplinary software development in electronic structure theory (MQM Poster)

At the beginning of the month, from 30th June till 5th July, I attended the 9th Molecular Quantum Mechanics Conference in my old home Heidelberg. This occasion was a great opportunity to catch up with friends and colleges both in science and from my old circle in Heidelberg as well …

read more# Modern software-development techniques in electronic structure theory

A few weeks ago, on 23rd May I received an invitation to visit the Laboratoire de Physique des Lasers, Atomes et Molécules at the Université de Lille and present about my recent work. When it came to selecting a topic, me and my host, Andre Gomes, quickly agreed to focus …

read more# Coulomb Sturmian basis functions in electronic structure theory

Earlier this month, on 3rd of May, I was invited for a day to the Laboratoire de Physique et Chimie Théoriques of the Université de Lorraine in Metz. Unlike my earlier stay in Metz stay, during the MES conference, last August, I did not manage to enjoy this beautiful city …

read more# Coulomb Sturmian basis functions in electronic structure theory

After my first Coulomb Sturmian-related talk at the LCT last November, I was approached by Julien Toulouse and asked whether I could give another talk providing a little more insight into Coulomb Sturmians and their potential.

A few weeks ago, on 29th March, it was thus about time for a …

read more# PostDoc position at CERMICS / Sorbonne Université

Last week I started my new position as a postdoctoral fellow at the MATHERIALS team of the Centre d'Enseignement et de Recherche en Mathématiques et Calcul Scientifique (CERMICS) laboratory and Inria Paris with an additional affiliation to the Institut des Sciences du Calcul et des Données at Sorbonne Université. As …

read more# SelfConsistentField.jl: A julia toolbox for coding self-consistent field algorithms

# Design of the molsturm quantum-chemistry framework

A few weeks ago, on 23rd November, I was invited to speak at the mathematics and chemistry seminar (GdT mathématiques et chimie) at Sorbonne Université in Paris. This seminar is a joint meeting of theoretical chemists and mathematicians from the LJLL (Laboratoire Jacques-Louis Lions) and the LCT (Laboratoire de Chimie …

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# Simulating chemistry: Enabling novel approaches for modelling the electronic structure of molecules

Last week Wednesday I was invited to present my research in front of a bunch of young researchers from the Heidelberg Laureate Forum visiting our institute. Whilst I would have loved to attend the full week of the forum, I am happy that in this way I was able to …

read more# Franco-German Workshop 2018: Open problems related to the algebraic-diagrammatic construction scheme

In some of my recent projects, e.g. the PE-ADC paper, I got a little more into method development surrounding the algebraic-diagrammatic construction scheme (ADC). Even though quite a few people from the Dreuw group in Heidelberg are involved with ADC development and we have regular talks on ADC, I …

read more# MES 2018 in Metz: molsturm Towards quantum-chemical method development for arbitrary basis functions

Currently I am attending the Molecular Electronic Structure 2018 conference in Metz, an electronic-structure theory conference intended for researchers working on novel methodologies, such as explicit correlation, density matrix theory, stochastic approaches or on discretisation techniques going beyond Gaussian-type orbitals.

Especially the latter aspect fits well to the kind of …

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# Coulomb Sturmians in electronic structure theory (Poster at 16th ICQC)

Last week from 18th till 23rd June I attended the 16th International Congress of Quantum Chemistry (ICQC) in Menton, France. Apart from the absolutely stunning scenery at the French Riviera as well as the historic conference building, the conference was a great opportunity to meet up and discuss with people …

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# Aachen: Beyond Gaussian-type orbitals

From Monday till Wednesday this week I was invited to the computational mathematics research group of Prof. Dr. Benjamin Stamm at the RWTH Aachen University. In retrospect I am very thankful for the invitation, since the three days turned out to be filled with fruitful discussions, scientific exchange and brainstorming …

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 …

read more# Oberwolfach workshop: Mathematical Methods in Quantum Chemistry

Last week I was invited to the Mathematical Research Institute Oberwolfach (Mathematisches Forschungsinstitut Oberwolfach) for a workshop about Mathematical Methods in Quantum Chemistry. I am really grateful to the organisers Eric Cancès, Gero Friesecke, Trygve Helgaker and Lin Lin for asking me to join this meeting as it turned out …

read more# Lazy matrices talk from the IWR school 2017

As mentioned in a previous post on this matter last month, from 2nd to 6th October, the IWR hosted the school Mathematical Methods for Quantum Chemistry, which I co-organised together with my supervisors Andreas Dreuw and Guido Kanschat as well as the head of my graduate school Michael Winckler.

From …

read more# Coulomb-Sturmians and molsturm

Yesterday I gave a talk at our annual group retreat at the Darmstädter Haus in Hirschegg, Kleinwalsertal. For this talk I expanded the slides from my lazy matrix talk in Kiel, incorporating a few of the more recent Coulomb-Sturmian results I obtained.

Most importantly I added a few slides to …

read more# IWR School: Mathematical Methods for Quantum Chemistry

From

read more**2nd to 6th October 2017**the IWR hosts the school Mathematical Methods for Quantum Chemistry, which aims at shining some light into the simulation of quantum chemical problems and their mathematical properties. I am very happy to be part of the organising committee for this school, especially since I …# Lazy matrices in quantum chemistry

On my way back from Copenhagen last Thursday I stopped in Kiel to visit Henrik Larsson and some other people from last year's Deutsche Schülerakademie in Grovesmühle.

Henrik is doing his PhD at the group of Prof. Bernd Hartke and so I took the opportunity and gave a short talk …

read more# HPC day at Niels Bohr Institute

# look4bas: Small script to search for Gaussian basis sets

In the past couple of days I hacked together a small Python script, which searches through the EMSL basis set exchange library of Gaussian basis sets via the commandline.

Unlike the webinterface it allows to use

read more`grep`

-like**regular expressions**for matching the names and descriptions of the basis sets …# The design of molsturm

Yesterday I was invited to the give a talk at the group seminar of Prof. Thomas Kühne at the University of Paderborn. I was really happy about this invitation, since this gave me a great opportunity to talk about the recent direction my PhD has taken.

Motivated from the problems …

read more# 51th Symposium on Theoretical Chemistry (Potsdam)

# [c¼h] Einführung in die Elektronenstrukturtheorie

The week before my bash scripting course I gave another short talk for the weekly meeting of the Heidelberg Chaostreff NoName e.V. Unlike last time the talk was not concerned with a traditional "Hacker" topic, but much rather I tried to give a brief introduction into my own research …

read more# A short return to Cambridge

About two weeks ago, on Friday the 13th of March, I was invited back to the Chemistry Department at the University of Cambridge. As part of their Theoretical Chemistry Informal Seminar talk series I was asked to give a short talk (Abstract) about my current research. Needless to say that …

read more# 50th Symposium on Theoretical Chemistry (Vienna)

Last month, from 14th to the 18th of September, I attended my first conference. Together with many members of my group I was at the 50th Symposium on Theoretical Chemistry in Vienna. It was a great opportunity to present my work, get feedback on some ideas and get to know …

read more# PhD Project: Finite Element Methods in Quantum Chemistry

In January I officially started my PhD in the Theoretical Chemistry group of Prof. Dr. Andreas Dreuw at the Interdisziplinäres Zentrum für wissenschaftliches Rechnen of the Ruprecht-Karls-Universität Heidelberg. The principle aim of the project is to replace the common formalism of using atom-centered basis functions (e.g. Gaussian atomic orbitals …

read more