About

Lan Cheng is an assistant professor in the Department of Chemistry at Johns Hopkins University, specializing in theoretical and computational chemistry. His research group focuses on relativistic electron-structure theory and heavy-element chemistry, developing novel electronic-structure methods and applying them to chemical and spectroscopic studies. His work aims to create quantum-chemical methods and computer programs that are generally applicable across the entire periodic table and to both ground and excited electronic states. A significant aspect of his research involves treating relativistic effects on molecular properties, addressing the challenges of accurately and efficiently incorporating relativistic effects into quantum-chemical calculations. His group works on algorithms and computer programs for relativistic effects in computations of molecular energies and properties, including electrical and magnetic properties and spin-orbit-dependent parameters, with applications to chemical and spectroscopic problems involving heavy elements such as coinage metals, lanthanides, and actinides.

Research topics

• Computer Science
• Physics
• Quantum mechanics
• Computational physics
• Data science
• Programming language

Selected publications

• Nuclear Schiff Moment of the Fluorine Isotope <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mmultiscripts> <mml:mrow> <mml:mi mathvariant="normal">F</mml:mi> </mml:mrow> <mml:mprescripts/> <mml:none/> <mml:mrow> <mml:mn>19</mml:mn> </mml:mrow> </mml:mmultiscripts> </mml:mrow> </mml:math>

  Physical Review Letters · 2026-02-26 · 1 citations

  articleOpen access

  Nuclear Schiff moments (NSMs) are sensitive probes for physics beyond the standard model of particle physics signaling violations of time-reversal and parity-inversion symmetries in atomic nuclei. In this Letter, we report the first-ever calculation of a NSM in a nuclear ab initio framework, employing the no-core shell model to study the fluorine isotope ^{19}F. We further perform quantum-chemistry calculations to evaluate the sensitivity of the hafnium monofluoride cation, HfF^{+}, to the NSM of ^{19}F. Combined with recent high-precision measurements of the molecular electric dipole moment of HfF^{+} [Roussy et al., An improved bound on the electron's electric dipole moment, Science 381, 46 (2023).SCIEAS0036-807510.1126/science.adg4084], our results enable the first experimental bound on the NSM of ^{19}F. Although the resulting bounds on the pion-nucleon-nucleon (πNN) coupling constants are not yet the most stringent, this Letter establishes the foundation for constraining πNN interactions using nuclear ab initio methods.

  PublisherOA PDFDOI

• Robust Performance of the Noniterative Triples Corrections in CCSD(T) _Λ : YbS as a Challenging Case with Strong Variation of Orbital Rotation

  The Journal of Physical Chemistry A · 2026-05-18

  articleSenior authorCorresponding

  A relativistic coupled-cluster study on the ytterbium monosulfide molecule (YbS) in synergy with a high resolution microwave spectroscopy study is reported. The quality of the potential energy surfaces and the surfaces of the nuclear electric quadrupole coupling constants (eQq’s) computed using relativistic exact two-component (X2C) coupled-cluster singles and doubles (CCSD), CCSD augmented with a noniterative treatment of triple excitations [CCSD(T)], and the “Λ”-version of CCSD(T) [CCSD(T)Λ] is carefully assessed, comparing computed structure parameters and eQq values to precise experimental benchmark values derived from the microwave rotational spectrum of vibrationally excited YbS. The X2C–CCSD calculations are shown to provide qualitatively accurate results, while CCSD(T)Λ calculations provide reliable triples corrections. The inaccuracy of the corresponding CCSD(T) calculations is attributed to a strong variation of orbital rotation due to the coupling between the Yb[4f146s0]S[2s22p6] and Yb[4f136s1]S[2s22p6] configurations along the potential energy surface.

  PublisherDOI

• Nuclear-electric-quadrupole-moment-induced parity doubling in molecules for symmetry-violation searches

  Physical review. A/Physical review, A · 2025-07-21

  articleOpen accessSenior author

  Searches for the nuclear magnetic quadrupole moment (MQM) and nuclear Schiff moment (NSM) have high discovery potential for violations of time ($T$) and parity ($P$) reversal symmetries beyond the Standard Model. Molecules containing heavy nuclei are typically used to enhance the sensitivity to MQMs and NSMs due to their strong internal electric fields and potential octupole deformation. To extract these effects in the laboratory frame, a bias electric field is required to polarize the molecule by mixing states of opposite parity (parity doublets). Typical heavy nuclei that are sensitive to symmetry-violation also possess large nuclear electric quadrupole moments (EQMs) when its nuclear spin is $I\geq1$. We show that EQMs can significantly modify the energy splitting between parity doublet states and thus change the required polarizing electric field. As a result, the EQM-induced energy splitting must be taken into account in designing such experiments. We provide qualitative estimates of parity doubling from EQMs and supporting \textit{ab initio} calculations, along with implications for candidate molecules in symmetry-violation searches.

  PublisherOA PDFDOI

• Integrated Experimental and Modeling Study of Persulfate-Based Oxidative Leaching and Electrodeposition for Copper Recovery from Waste Printed Circuit Boards

  SSRN Electronic Journal · 2025-01-01

  preprintOpen access
  PublisherDOI

• Resonant x-ray emission across the L₃ edge of uranium compounds

  Journal of Physics B Atomic Molecular and Optical Physics · 2025-01-21 · 4 citations

  articleOpen access

  Abstract A narrow bandwidth x-ray beamline and a multi-crystal von Hamos spectrometer were used to record x-ray absorption and x-ray emission (XES) across the uranium L 3 edge of UO 2 , UO 3 , Cs 2 UO 2 Cl 4 , and Cs 2 UCl 6 . Measurements were made over 17150–17250 eV with an instrumental resolution of ∼2 eV. This resolution allowed the use of Lorentzian peak fits to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>5</mml:mn> </mml:msub> </mml:mrow> </mml:math> characteristic x-ray fluorescence lines that have ∼12–13 eV lifetime widths. The fluorescence yields of the four compounds display strong white lines near threshold and multiple scattering features at higher energies. The XES spectra were fit with three Lorentzians, two for the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>4</mml:mn> </mml:msub> </mml:mrow> </mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>5</mml:mn> </mml:msub> </mml:mrow> </mml:math> lines and one for inelastic scattering by 2 p –6 d excitations and 4 d –6 d final states. The intensities of the white lines were largely due to the inelastic scattering component. To support the measurements, relativistic equation-of-motion coupled-cluster and restricted active space configuration interaction calculations were performed for uranium core-excitation energies in Cs 2 UO 2 Cl 4 and Cs 2 UCl 6 . These calculations with rigorous treatments of relativistic effects are shown to provide accurate uranium L 3 -edge binding energies, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>L</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>N</mml:mi> <mml:mn>5</mml:mn> </mml:msub> </mml:mrow> </mml:math> emission energies, as well as the energy losses in the inelastic scattering process. The measured and calculated results show variations between compounds with U(IV) oxidation states that contain 6d 0 5f 2 electrons in their ground configurations (UO 2 and Cs 2 UCl 6 ) compared with U(VI) compounds (UO 3 and Cs 2 UO 2 Cl 4 ) with empty 5f and 6d configurations.

  PublisherDOI

• Analytic Evaluation of Energy First Derivatives for Cholesky Decomposition-Based Relativistic Two-Component Coupled-Cluster Methods

  Journal of Chemical Theory and Computation · 2025-11-12

  articleSenior authorCorresponding

  provides accurate results. Calculations for Mössbauer spectroscopy parameters of gold-containing complexes are reported to demonstrate the applicability of the present implementation to medium-sized molecules containing heavy atoms.

  PublisherDOI

• Integrated experimental and modeling study of persulfate-based oxidative leaching and electrodeposition for copper recovery from waste printed circuit boards

  Journal of environmental chemical engineering · 2025-10-09 · 3 citations

  article
  PublisherDOI

• Singlet-Fission Dynamics Modified through Templated Organic Semiconductor Crystallization

  ChemRxiv · 2025-11-12

  article

  Singlet fission (SF) is a process of multiexciton generation in molecular semiconductor materials that holds promise for improving light-to-charge conversion efficiencies in photovoltaic devices. Molecular packing structure is well-known to impact the electronic coupling that underlies triplet-pair generation, as well as pair separation and triplet transport that occur through singlet fission, ultimately affecting the potential to increase conversion efficiencies in light-harvesting devices. We previously demonstrated that templating the crystallization of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) films on a series of lead-halide perovskites provides a means to control intermolecular packing and alter the kinetics of triplet-pair separation and recombination. Here we contrast triplet transport with the ultrafast interconversion of the singlet exciton to the correlated triplet pair and the dependence of these processes on template-modified crystal packing. We observe that rate constants for the conversion of singlet excitons to correlated triplet pairs likewise are sensitive to the template structure but with a trend that is anticorrelated with those for triplet-pair separation and triplet-triplet annihilation. This observation is consistent with the divergent requisite frontier orbital overlap symmetries of adjacent chromophores that underlie the electronic coupling associated with the generation of triplet pairs and the subsequent triplet transport. We examine how the template-dependent packing structures, as determined by molecular dynamics simulations of a film-template interface, alter figures of merit for electronic interactions (estimated by frontier-orbital overlaps) that underlie each step of the SF mechanism. Our results demonstrate that templating is a general platform for tuning the relative rates of deactivation of correlated triplet pairs in SF-active materials with the potential to favor higher triplet-pair yields or for assisting singlet-mediated triplet-transfer mechanisms without structural modification of the SF-active chromophore.

  PublisherDOI

• Electronic spectroscopy and excited state mixing of OThF

  The Journal of Chemical Physics · 2025-01-10 · 1 citations

  articleSenior author

  Electronic spectra for OThF have been recorded using fluorescence excitation and two-photon resonantly enhanced ionization techniques. Multiple vibronic bands were observed in the 340-460 nm range. Dispersed fluorescence spectra provided ground state vibrational constants and evidence of extensive vibronic state mixing at higher excitation energies. Two-photon ionization measurements established the ionization energy for OThF of 6.283(5) eV. To guide the assignment of the OThF spectra, electronic structure calculations were carried out using relativistic equation-of-motion coupled-cluster singles and doubles methods. These calculations indicated that spin-orbit induced mixing of the 32A″ and 42A' states was mediated by a seam of potential energy surface intersections.

  PublisherDOI

• Singlet-Fission Dynamics Modified through Templated Organic Semiconductor Crystallization

  ChemRxiv · 2025-10-15

  preprint

  Singlet fission (SF) is a process of multiexciton generation in molecular semiconductor materials that holds promise for improving light-to-charge conversion efficiencies in photovoltaic devices. Molecular packing structure is well-known to impact the electronic coupling that underlies triplet-pair generation, as well as pair separation and triplet transport that occur through singlet fission, ultimately affecting the potential to increase conversion efficiencies in light-harvesting devices. We previously demonstrated that templating the crystallization of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-Pn) films on a series of lead-halide perovskites provides a means to control intermolecular packing and alter the kinetics of triplet-pair separation and recombination. Here we contrast triplet transport with the ultrafast interconversion of the singlet exciton to the correlated triplet pair and the dependence of these processes on template-modified crystal packing. We observe that rate constants for the conversion of singlet excitons to correlated triplet pairs likewise are sensitive to the template structure but with a trend that is anticorrelated with those for triplet-pair separation and triplet-triplet annihilation. This observation is consistent with the divergent requisite frontier orbital overlap symmetries of adjacent chromophores that underlie the electronic coupling associated with the generation of triplet pairs and the subsequent triplet transport. We examine how the template-dependent packing structures, as determined by molecular dynamics simulations of a film-template interface, alter figures of merit for electronic interactions (estimated by frontier-orbital overlaps) that underlie each step of the SF mechanism. Our results demonstrate that templating is a general platform for tuning the relative rates of deactivation of correlated triplet pairs in SF-active materials with the potential to favor higher triplet-pair yields or for assisting singlet-mediated triplet-transfer mechanisms without structural modification of the SF-active chromophore.

  PublisherDOI

Recent grants

• Accurate Electronic and Vibrational Structure Calculations of Metal-Containing Small Molecules of Importance to Precision Measurement and Laser Cooling

  NSF · $413k · 2020–2023

• Accurate Electronic and Vibrational Structure Calculations of Metal-Containing Small Molecules of Importance to Precision Measurement and Laser Cooling

  NSF · $436k · 2023–2026

Frequent coauthors

• Wenjian Liu

  First Affiliated Hospital of Anhui Medical University

  72 shared

• John M. Doyle

  49 shared

• Jürgen Gauß

  Johannes Gutenberg University Mainz

  48 shared

• Yunlong Xiao

  Peking University

  45 shared

• Zack Lasner

  44 shared

• John F. Stanton

  University of Florida

  43 shared

• Benjamin L. Augenbraun

  41 shared

• Stella Stopkowicz

  Saarland University

  38 shared