Jonathan and Petra's paper Conductivity of an electron coupled to anharmonic phonons is posted to the arXiv. We use mixed quantum-classical Ehrenfest dynamics to study the impact of anharmonicity and to evaluate several simpler theories.
James's paper The normal state of attractive Fermi gases from coupled-cluster theory, in collaboration with John Sous, is posted to the arXiv. In a new direction for the group, we demonstrate the successes, struggles, and promise of CC theory for this form of interacting quantum matter.
Congratulations to Sam, who is awarded the Chemistry Department's Pegram Award, given to graduate students in their final year, in recognition of meritorious achievements in chemical research!
Yeongsu and Sylvia's paper Simplified GW/BSE Approach for Charged and Neutral Excitation Energies of Large Molecules and Nanomaterials is published in J. Chem. Theory Comput.! Update: And featured on the cover!
Tim is promoted to Associate Professor of Chemistry with tenure, effective July 1, 2022. Since the start of our group in 2016, it's been a wild and unpredictable six years. This milestone would never have been possible without incredible students, postdocs, and colleagues at the University of Chicago, Columbia, and the Flatiron Institute. 🙏
Congratulations to Xiao, who will be starting in July 2022 as an Assistant Professor in the Department of Chemistry & Biochemistry at UC Santa Cruz!
Verena and Hong-Zhou's paper Ground-state properties of metallic solids from ab initio coupled-cluster theory is posted to the arXiv. We evaluate the performance of CCSD and some extensions for solid lithium and aluminum—quite a challenge for wavefunction-based quantum chemistry! This work is part of the Columbia Center for Computational Electrochemistry.
Hong-Zhou's paper Correlation-consistent Gaussian basis sets for solids made simple is published in J. Chem. Theory Comput.!
Describing a new QMC method for excited states, applicable to active spaces with up to 100 orbitals, Sam and James's paper Full Configuration Interaction Excited-State Energies in Large Active Spaces from Randomized Subspace Iteration is posted to the arXiv.
Sylvia's paper Full-frequency dynamical Bethe-Salpeter equation without frequency and a study of double excitations is published in J. Chem. Phys.
An important step towards making correlated calculations for solids as reliably predictive as those for molecules, Hong-Zhou's paper Correlation-consistent Gaussian basis sets for solids made simple is posted to the arXiv. We're happy to share the alpha version of our GTH basis sets while our manuscript is under review—just ask!
Norah and Xiao's paper Linear free energy relationships in electrostatic catalysis is posted to the arXiv. This work is part of the Columbia NSF CCI for Chemistry with Electric Fields.
Welcome to Yu Hsuan (Jason) Liang, who joins the group as a first-year PhD student! Before coming to Columbia, Jason received his BS in Chemistry at UC Berkeley, where he performed research in the Head-Gordon group.
Following her previous work on Full-frequency GW without frequency, Sylvia's latest paper Full-frequency dynamical Bethe-Salpeter equation without frequency and a study of double excitations is posted to the arXiv.
Hong-Zhou's paper Tight distance-dependent estimators for screening two-center and three-center short-range Coulomb integrals over Gaussian basis functions is published in J. Chem. Phys.!
Yeongsu and Sylvia's paper A simplified GW/BSE approach for charged and neutral excitation energies of large molecules and nanomaterials is posted to the arXiv! Exhausted with building semiempirical models by hand (like in this paper), we have long wanted a cheap, black-box method.
Petra's paper Anharmonic Lattice Dynamics from Vibrational Dynamical Mean-Field Theory is posted to the arXiv! A new embedding approach for interacting phonons, VDMFT is exact in the harmonic and molecular limits, nonperturbative, systematically improvable, and applicable to classical or quantum nuclei.
Congratulations to Tami, who has accepted a faculty position in the Materials Science and Engineering program at Bar-Ilan University, where she will start in January 2022!
Malte's paper Improving MP2 band gaps with low-scaling approximations to EOM-CCSD is published in J. Chem. Phys. and selected as an Editor's Pick.
One week, two new doctors! Yeongsu defends her thesis "Semiempirical methods for excited states of nanomaterials" and Jonathan defends his thesis "Dynamics and spectroscopy of strongly coupled electrons and nuclei". Congratulations Dr. Cho and Dr. Fetherolf!
Hong-Zhou's paper Tight distance-dependent estimators for screening two-center and three-center short-range Coulomb integrals over Gaussian basis functions is posted to the arXiv. The results in the paper are general but were needed by us to bring increased speed and robustness to our periodic range-separated Gaussian density fitting.
Because there's so much more to life beyond the first excited state, Xiao's paper Absorption Spectra of Solids from Periodic Equation-of-Motion Coupled-Cluster Theory is posted to the arXiv.
Welcome to LaToya Anderson (Brooklyn College) and Ellie Mackintosh (Davidson College) who join the group as CCQ summer interns!
James and Malte's paper Dynamical correlation energy of metals in large basis sets from downfolding and composite approaches is published in J. Chem. Phys.!
A little bit of third-order perturbation theory goes a long way. Malte's paper Improving MP2 band gaps with low-scaling approximations to EOM-CCSD is posted to the arXiv.
Malte successfully defends his thesis, "Wave function-based electronic structure theory for solids." Congratulations Dr. Lange!
Yeongsu and Sam's paper Simulations of Trions and Biexcitons in Layered Hybrid Organic-Inorganic Lead Halide Perovskites is published in Phys. Rev. Lett.!
Sam is selected as an awardee of the DOE Office of Science Graduate Student Research (SCGSR) program, which will take him to Berkeley Lab for the final year of his PhD!
Hong-Zhou's paper Fast periodic Gaussian density fitting by range separation is published in J. Chem. Phys., demonstrating a 10x speedup over previous implementations.
Sam's paper Approximating matrix eigenvalues by randomized subspace iteration is posted to the arXiv. It presents a general approach that we use to design a projector Monte Carlo method for excited states.
Congratulations to Yeongsu for receiving the Spring 2021 ACS COMP Chemical Computing Group Excellence Award!
Rescuing MP2 theory for periodic metals, James and Malte's paper Dynamical correlation energy of metals in large basis sets from downfolding and composite approaches is posted to the arXiv!
Tim will teach Electronic Structure Theory at the 2021 Telluride School on Theoretical Chemistry, to be held virtually July 19-23. More information and a link to apply can be found here.
Jonathan's paper Vibrational heat-bath configuration interaction is published in J. Chem. Phys.!
Hong-Zhou's paper Fast periodic Gaussian density fitting by range separation is posted to the arXiv!
Sylvia's paper Full-frequency GW without frequency is published in J. Chem. Phys.!
The first of the new year: Bryan's paper Regional Embedding Enables High-Level Quantum Chemistry for Surface Science, a collaboration with Gerald Knizia, is published in J. Phys. Chem. Lett. and featured on the cover!
A great collaboration with the Nuckolls and Roy groups at Columbia featuring topological band structure characterization by Yeongsu, Polytypism, Anisotropic Transport, and Weyl Nodes in the van der Waals Metal TaFeTe4 is published in JACS!
Welcome to Ethan Vo, who joins the group as a first-year graduate student! Before coming to Columbia, Ethan was an undergraduate at the University of Washington.
A new paper from Jonathan is posted to the arXiv! Vibrational heat-bath configuration interaction can efficiently calculate anharmonic vibrational spectra of large molecules with sub-wavenumber accuracy.
Yeongsu and Sam team-up, comparing large variational calculations and diffusion Monte Carlo for Simulations of Trions and Biexcitons in Layered Hybrid Organic-Inorganic Lead Halide Perovskites!
Bryan's paper, Regional Embedding Enables High-Level Quantum Chemistry for Surface Science, a collaboration with Gerald Knizia, is posted to the arXiv!
Sylvia's paper, Full-Frequency GW without Frequency, is posted to the arXiv!
Welcome back to postdoc James Smith (Ph.D. CU Boulder, Sharma group), who returns to CCQ as a Flatiron Research Fellow after spending summer 2019 as a CCQ Summer Intern.
Malte's paper, Active space approaches combining coupled-cluster and perturbation theory for ground states and excited states, is published in a special issue of Molecular Physics in honor of Jürgen Gauss.
Sam's paper, Improved Fast Randomized Iteration Approach to Full Configuration Interaction, is published in J. Chem. Theory Comput.
Bryan's paper Quantum plasmons and intraband excitons in doped nanoparticles: Insights from quantum chemistry is published in J. Chem. Phys.!
Congratulations to Yeongsu for receiving the Columbia Chemistry department's 2020-2021 Kathy Chen Fellowship, which is awarded to a rising fifth year student in recognition of that student's distinguished achievements and potential!
Sam's paper, Improved Fast Randomized Iteration Approach to Full Configuration Interaction, with Rob Webber and Jonathan Weare, is posted to the arXiv.
Jonathan's paper, A unification of the Holstein polaron and dynamic disorder pictures of charge transport in organic crystals, is accepted for publication in Physical Review X!
Excitons in Solids from Periodic Equation-of-Motion Coupled-Cluster Theory is published in J. Chem. Theory Comput. Congrats Xiao and great work!
Tim is appointed to the Early Career Editorial Advisory Board of the Journal of Chemical Physics.
Alan's paper, Ab Initio Linear and Pump-Probe Spectroscopy of Excitons in Molecular Crystals, is published in J. Phys. Chem. Letters! Awesome work Alan!
Summarizing the design philosophy, features, and impact, Recent developments in the PySCF program package is posted to the arXiv. This article describes the state of PySCF v1.7.1, the final version before v2.0 - coming soon!
Xiao's paper, Excitons in solids from periodic equation-of-motion coupled-cluster theory, is posted to the arXiv. Across eight semiconductors and insulators, EOM-CCSD predicts first excitation energies with a mean absolute error of 0.27 eV!
Tim and Michael Thoss served as Guest Editors for a Special Topic on the dynamics of open quantum systems in the Journal of Chemical Physics. Read the preface here.
Sam is selected as a MolSSI Investment Software Fellow. Congrats Sam!
Welcome to Sylvia Bintrim (B.S. Penn State) and Petra Shih (B.S., M.S. National Taiwan University), who join the group as first-year Ph.D. students!
Holstein or Peierls? Why choose? Jonathan's paper with Denis Golez from CCQ, A unification of the Holstein polaron and dynamic disorder pictures of charge transport in organic semiconductors, is posted to the arXiv.
Welcome to Giulia Biffi, a visiting Ph.D. student from Roman Krahne's group at the Italian Institute of Technology!
Yeongsu's work, Optical Properties of Layered Hybrid Organic-Inorganic Halide Perovskites: A Tight-Binding GW-BSE Study, is published in J. Phys. Chem. Letters — an accurate but efficient approach for band gaps and excitons in complex, heterogeneous materials with large unit cells!
Alan's paper, Ab Initio Linear and Pump-Probe Spectroscopy of Excitons in Molecular Crystals, is posted to the arXiv — the first application of atomistic periodic EE-EOM-CCSD!
A great collaboration with the Weiss (Northwestern) and Darancet (ANL) groups, Large Band Edge Tunability in Colloidal Nanoplatelets, is published in Nano Letters.
Welcome to our newest Columbia postdoc, Tamar Goldzak! Tami previously completed her Ph.D. with Nimrod Moiseyev at the Technion and was a postdoc with Troy Van Voorhis at MIT.
Yeongsu's paper, Thickness-dependent optical properties of layered hybrid organic-inorganic halide perovskites: A tight-binding GW-BSE study is posted to the arXiv!
A great collaboration featuring Yeongsu's theory, Dielectric disorder in two-dimensional materials is published in Nature Nanotechnology.
Beyond Walkers in Stochastic Quantum Chemistry: Reducing Error using Fast Randomized Iteration is published in J. Chem. Theory Comput. Great work Sam!
A collaboration with Roel Tempelaar, Many-body simulation of two-dimensional electronic spectroscopy of excitons and trions in monolayer transition metal dichalcogenides is published in Nature Communications.
Bryan's paper Quantum plasmons and intraband excitons in doped nanoparticles: Failure of the Tamm-Dancoff approximation and importance of electron-hole attraction is posted to the arXiv!
Tim receives the Presidential Early Career Award for Scientists and Engineers (PECASE). Thank you to the AFOSR for the nomination and for supporting our research! [Columbia Science News]
Tim is named the winner of the 2019 Hermann Kuemmel Early Achievement Award in Many-Body Physics, "for making possible the determination of condensed phase spectra within the framework of coupled cluster theory, and for elucidating the relationship between excited-state coupled cluster theory and Green’s function diagrammatic approximations." Honored to have our work on coupled cluster recognized by an award named for one of its pioneers!
Alan's paper, Ab Initio Lifetime and Concomitant Double-Excitation Character of Plasmons at Metallic Densities, is published in Phys. Rev. Lett.
Congratulations to Sam, who was selected as a 2019 MolSSI Seed Software Fellow!
Welcome to our summer researchers, Sylvia Bintrim and James Smith! Sylvia is an incoming PhD student at Columbia and an NSF Graduate Research Fellow. James is a summer intern at CCQ, visiting from CU Boulder, where he is a PhD student in the Sharma group.
A collaboration long in the making: Coupled-cluster impurity solvers for dynamical mean-field theory is posted to the arXiv.
Sam's paper, with Rob Webber and Jonathan Weare of NYU, Beyond Walkers in Stochastic Quantum Chemistry: Reducing Error using Fast Randomized Iteration, is posted to the arXiv - the group's first foray into QMC!
Alan's paper, Vertex Corrections to the Polarizability Do Not Improve the GW Approximation for the Ionization Potential of Molecules, is published in J. Chem. Theory Comput.
Congratulations to James for being selected to receive a 2019 NSF Graduate Research Fellowship! UPDATE: And the National Defense Science and Engineering Graduate Fellowship (NDSEG)! Tough choice.
Happy International Women's Day! Here's Yeongsu presenting her work on excitons in Ruddlesden-Popper perovskites at the APS March Meeting. According to IPEDS and the APS, only 40% of PhDs in chemistry and 20% of PhDs in physics are earned by women. Many resources available from the ACS Women Chemists Committee, the APS Women in Physics initiative, and the APS STEP UP 4 Women program.
At the APS March meeting, kicking off our Focus Session, "Periodic quantum chemistry beyond DFT," co-organized with Garnet Chan. Sessions include "DFT, embedding, and beyond," "Quantum Monte Carlo," and "Wavefunction methods."
Xiao Wang joins CCQ as a Flatiron Research Fellow. Previously, Xiao received his Ph.D. with Fritz Schaefer at the University of Georgia and was a postdoc with Ed Valeev at Virginia Tech. Welcome Xiao!
Random-phase approximation excitation energies from approximate equation-of-motion coupled-cluster doubles is selected for the 2018 JCP Editors' Choice, "a few of the many notable JCP articles of 2018 that present significant and definitive research in experimental and theoretical areas of the field."
The group is moving to New York City! Tim has accepted a joint position in the Department of Chemistry at Columbia University and the newly-established Center for Computational Quantum Physics at the Flatiron Institute, a division of the Simons Foundation.
Alan's second paper in as many weeks - this time, plasmon excitations in metals from equation-of-motion coupled-cluster theory. Ab Initio Lifetime and Concomitant Double-Excitation Character of Plasmons at Metallic Densities is posted to the arXiv.
Tim's paper with Roel Tempelaar, Many-Body Simulation of Two-Dimensional Electronic Spectroscopy of Excitons and Trions in Monolayer Transition-Metal Dichalcogenides, is posted to the arXiv.
Combining wavefunction-based quantum chemistry with Green's function techniques: Alan's paper, Vertex corrections to the polarizability do not improve the GW approximation for molecules, is posted to the arXiv.
Tim's paper, Random-phase approximation excitation energies from approximate equation-of-motion coupled-cluster doubles, is published as a Communication in J. Chem. Phys. and selected as an Editor's Pick.
Malte's paper, On the Relation Between Equation-of-Motion Coupled-Cluster Theory and the GW Approximation, is published in J. Chem. Theory Comput.!
Really going to miss having this guy in the group. Good luck at Caltech, Shi-Ning!
Shi-Ning presents his undergraduate thesis, "Classical and quantum theories for screened Coulomb interactions" and is chosen to receive the Norman H. Nachtrieb Memorial Award for Excellence in Undergraduate Studies in Chemistry. Congrats Shi-Ning!
Congratulations to Sam, maybe the first theoretical chemistry student to win the Gerhard Closs Teaching Award in Organic Chemistry!
Malte's paper, On the Relation Between Equation-of-Motion Coupled-Cluster Theory and the GW Approximation, appears on the arXiv. They're not as different as you may think! IP/EA-EOM-CCSD contains (most of) the physics described by the GW approximation, but many additional effects that improve the accuracy.
Congratulations to Jonathan and Malte, who have been selected as 2018 NSF Graduate Research Fellows!
Tim's paper, Random-phase approximation excitation energies from approximate equation-of-motion ring coupled-cluster doubles, is posted to the arXiv.
Many thanks to the students of BU, MIT, and Harvard, who hosted Tim for the Greater Boston Area Theoretical Chemistry Lecture Series and three exciting days of scientific discussions.
Yeongsu's paper, Environmentally sensitive theory of electronic and optical transitions in atomically thin semiconductors, is published as a Rapid Communication in Phys. Rev. B, and selected as an Editors' Suggestion!
Congratulations to Yeongsu, Jonathan, and Malte, who have all passed their second-year candidacy exams!
Jonathan's paper, Linear and nonlinear spectroscopy from quantum master equations, is published in J. Chem. Phys.
Two new graduate students join the group! Welcome to Sam Greene (B.S. UChicago, M.Sc. Oxford), who will be jointly advised by Jonathan Weare (UChicago Statistics), and James Callahan (B.A. Harvard).
Tim is selected for the US Air Force Young Investigator Program (YIP), which will fund our work on exciton interactions in semiconductor nanostructures. The objective of the Air Force YIP is "to foster creative basic research in science and engineering, enhance early career development of outstanding young investigators, and increase opportunities for the young investigators to recognize the Air Force mission and the related challenges in science and engineering."
Alan Lewis (D. Phil. Oxford University) joins the group as a postdoctoral researcher. Welcome, Alan!
Quantum master equations: time-tested classics for single-time observables, but how good are they for multi-time correlation functions, like the ones probed in spectroscopy? Read Jonathan's paper, Linear and nonlinear spectroscopy from quantum master equations, to find out!
Can we use atomically-thin semiconductors as optical sensors of the local chemical environment? Read Yeongsu's paper, Environmentally-Sensitive Theory of Electronic and Optical Transitions in Atomically-Thin Semiconductors, to find out why it's harder than you think!
Farewell to pseudopotentials! Gaussian and plane-wave mixed density fitting for periodic systems has been posted to the arXiv.
We have received a Start-Up Research Grant from the US-Israel Binational Science Foundation to study the role of low-frequency nuclear fluctuations in soft semiconductors in collaboration with Omer Yaffe's group at the Weizmann Institute!
Bryan Lau (Ph.D. Northwestern University) joins the group as a postdoctoral researcher. Welcome, Bryan!
Malte receives the Nathan Sugarman Teaching Award in General Chemistry!
University of Chicago undergraduate Shi-Ning Sun joins the group!
Tim visits nearby Northwestern and gives a talk at the Northwestern-Argonne Solar Energy Research Center (ANSER).
Tim and Greg Scholes organize a Focus session on Spectroscopy and Dynamics of Multichromophore Systems at APS March Meeting.
Gaussian-Based Coupled-Cluster Theory for the Ground State and Band Structure of Solids has been accepted for publication in the Journal of Chemical Theory and Computation.
We contribute to the open-source PySCF software package, especially concerning excited-state and condensed-phase electronic structure. A preprint describing the capabilities and design philosophy of PySCF has been posted to the arXiv: The Python-based Simulations of Chemistry Framework (PySCF).
Tim gives an invited talk at the 18th Total Energy and Force Methods workshop, held at ICTP.