{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,21]],"date-time":"2026-10-21T03:37:04Z","timestamp":1792553824149,"version":"4.5.0"},"reference-count":89,"publisher":"AIP Publishing","issue":"15","license":[{"start":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T00:00:00Z","timestamp":1792454400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002661","name":"Fonds de la Recherche Scientifique\u2013FNRS","doi-asserted-by":"publisher","award":["2.5020.11"],"award-info":[{"award-number":["2.5020.11"]}],"id":[{"id":"10.13039\/501100002661","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100014690","name":"Ministerium f\u00fcr Kultur und Wissenschaft des Landes Nordrhein-Westfalen","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100014690","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100016132","name":"Gouvernement Wallon","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100016132","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2026,10,21]]},"abstract":"<jats:p>The std2 modular program package is dedicated to the computation of excited states and molecular response properties using simplified quantum chemistry approaches. The framework involves several variants of the simplified time-dependent density functional theory, including sTDA, sTD-DFT, SF-sTD-DFT, XsTDA, XsTD-DFT, and SF-XsTD-DFT methods. Combining controlled approximations with efficient implementations, the std2 program enables routine calculations on systems containing thousands of atoms while retaining a favorable balance between computational cost and predictive accuracy. Therefore, the framework supports all-atom quantum mechanics (AQM) methodologies for the treatment of surrounding and dynamical structural effects considering realistic systems. In this contribution, the capabilities of the std2 package are illustrated for spectroscopic observables, such as one- and two-photon absorption, electronic circular dichroism, optical rotation, second-harmonic generation, and excited-state absorption. Among results, benchmark calculations show that the recent XsTD-DFT scheme improves the description of excited states relative to sTD-DFT especially, for charge-transfer excitations while preserving a speedup of two to three orders of magnitude compared to standard TD-DFT. Applications of AQM methodologies to explicitly solvated systems and ultra-large systems are also highlighted, showing the adequacy of the std2 program to treat such systems. Overall, std2 provides an efficient platform for large-scale excited-state and spectroscopic simulations, especially in AQM protocols.<\/jats:p>","DOI":"10.1063\/5.0349975","type":"journal-article","created":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T12:02:03Z","timestamp":1792497723000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":1,"title":["The\n                    <tt>std2<\/tt>\n                    package: A computationally efficient program to calculate molecular response properties and excited states using simplified quantum chemistry methods"],"prefix":"10.1063","volume":"165","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3723-3257","authenticated-orcid":false,"given":"Pierre","family":"Beaujean","sequence":"first","affiliation":[{"name":"Theoretical Chemistry Laboratory, Unit of Theoretical and Structural Physical Chemistry, Namur Institute of Structured Matter (NISM), University of Namur 1 , Rue de Bruxelles, 61, B-5000 Namur,","place":["Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0000-8567-0043","authenticated-orcid":false,"given":"Axel","family":"Liger","sequence":"additional","affiliation":[{"name":"Theoretical Chemistry Group, Molecular Chemistry, Materials and Catalysis Division (MOST), Institute of Condensed Matter and Nanosciences, Universit\u00e9 Catholique de Louvain 2 , Louvain-la-Neuve B-1348,","place":["Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-6892-957X","authenticated-orcid":false,"given":"Arya","family":"Satisha","sequence":"additional","affiliation":[{"name":"Theoretical Chemistry Group, Molecular Chemistry, Materials and Catalysis Division (MOST), Institute of Condensed Matter and Nanosciences, Universit\u00e9 Catholique de Louvain 2 , Louvain-la-Neuve B-1348,","place":["Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-3877-6546","authenticated-orcid":false,"given":"Maril\u00f9 G.","family":"Maraldi","sequence":"additional","affiliation":[{"name":"Theoretical Chemistry Group, Molecular Chemistry, Materials and Catalysis Division (MOST), Institute of Condensed Matter and Nanosciences, Universit\u00e9 Catholique de Louvain 2 , Louvain-la-Neuve B-1348,","place":["Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3242-496X","authenticated-orcid":false,"given":"Christoph","family":"Bannwarth","sequence":"additional","affiliation":[{"name":"Institute of Physical Chemistry, RWTH Aachen University 3 , Melatener Str. 20, Aachen D-52074,","place":["Germany"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9564-7303","authenticated-orcid":false,"given":"Marc","family":"de Wergifosse","sequence":"additional","affiliation":[{"name":"Theoretical Chemistry Group, Molecular Chemistry, Materials and Catalysis Division (MOST), Institute of Condensed Matter and Nanosciences, Universit\u00e9 Catholique de Louvain 2 , Louvain-la-Neuve B-1348,","place":["Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2026,10,20]]},"reference":[{"key":"2026102008015511200_c1","doi-asserted-by":"publisher","first-page":"e202205735","DOI":"10.1002\/ange.202205735","article-title":"Best-practice DFT protocols for basic molecular computational chemistry","volume":"134","year":"2022","journal-title":"Angew. Chem."},{"key":"2026102008015511200_c2","doi-asserted-by":"publisher","first-page":"e1493","DOI":"10.1002\/wcms.1493","article-title":"Extended tight-binding quantum chemistry methods","volume":"11","year":"2021","journal-title":"Wiley Interdiscip. Rev.: Comput. Mol. Sci."},{"key":"2026102008015511200_c3","doi-asserted-by":"publisher","first-page":"e1695","DOI":"10.1002\/wcms.1695","article-title":"Simplified quantum chemistry methods to evaluate non-linear optical properties of large systems","volume":"14","year":"2024","journal-title":"Wiley Interdiscip. Rev.: Comput. Mol. Sci."},{"key":"2026102008015511200_c4","doi-asserted-by":"publisher","first-page":"145","DOI":"10.1002\/wcms.1161","article-title":"Semiempirical quantum-chemical methods","volume":"4","year":"2014","journal-title":"Wiley Interdiscip. Rev.: Comput. Mol. Sci."},{"key":"2026102008015511200_c5","doi-asserted-by":"publisher","first-page":"111","DOI":"10.1007\/bf00528484","article-title":"An intermediate neglect of differential overlap technique for spectroscopy: Pyrrole and the azines","volume":"32","year":"1973","journal-title":"Theor. Chim. Acta"},{"key":"2026102008015511200_c6","first-page":"313","article-title":"Semiempirical molecular orbital methods","volume-title":"Reviews in Computational Chemistry","year":"1991"},{"key":"2026102008015511200_c7","doi-asserted-by":"publisher","first-page":"1179","DOI":"10.1103\/physreva.20.1179","article-title":"Origin of the nonlinear second-order optical susceptibilities of organic systems","volume":"20","year":"1979","journal-title":"Phys. Rev. A"},{"key":"2026102008015511200_c8","doi-asserted-by":"publisher","first-page":"2527","DOI":"10.1063\/1.444123","article-title":"Calculations of induced moments in large molecules. II. Polarizabilities and second hyperpolarizabilities of some polyenes","volume":"77","year":"1982","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c9","doi-asserted-by":"publisher","first-page":"2536","DOI":"10.1063\/1.444124","article-title":"Calculations of induced moments in large molecules. III. Polarizabilities and second hyperpolarizabilities of some aromatics","volume":"77","year":"1982","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c10","doi-asserted-by":"publisher","first-page":"427","DOI":"10.1007\/bf00549035","article-title":"Calculations of induced moments in large molecules I. Polarizabilities and second hyperpolarizabilities in some alkanes","volume":"61","year":"1982","journal-title":"Theor. Chim. Acta"},{"key":"2026102008015511200_c11","doi-asserted-by":"publisher","first-page":"6766","DOI":"10.1103\/physrevb.28.6766","article-title":"Dispersion of the nonlinear second-order optical susceptibility of organic systems","volume":"28","year":"1983","journal-title":"Phys. Rev. B"},{"key":"2026102008015511200_c12","doi-asserted-by":"publisher","first-page":"1179","DOI":"10.1039\/f29858101179","article-title":"Calculation of the second-order electronic polarizabilities of some organic molecules. Part 1","volume":"81","year":"1985","journal-title":"J.\u00a0Chem. Soc., Faraday Trans. 2"},{"key":"2026102008015511200_c13","doi-asserted-by":"publisher","first-page":"1357","DOI":"10.1039\/p29870001357","article-title":"Non-linear optical properties of organic molecules. Part 3. Effect of substituents on the calculated hyperpolarisability of monosubstituted benzenes","volume":"16","year":"1987","journal-title":"J.\u00a0Chem. Soc., Perkin Trans. 2"},{"key":"2026102008015511200_c14","doi-asserted-by":"publisher","first-page":"4899","DOI":"10.1021\/ja00457a004","article-title":"Ground states of molecules. 38. The MNDO method. Approximations and parameters","volume":"99","year":"1977","journal-title":"J.\u00a0Am. Chem. Soc."},{"key":"2026102008015511200_c15","doi-asserted-by":"publisher","first-page":"3902","DOI":"10.1021\/ja00299a024","article-title":"Development and use of quantum mechanical molecular models. 76. AM1: A new general purpose quantum mechanical molecular model","volume":"107","year":"1985","journal-title":"J.\u00a0Am. Chem. Soc."},{"key":"2026102008015511200_c16","doi-asserted-by":"publisher","first-page":"775","DOI":"10.1002\/jcc.540140704","article-title":"Beyond the MNDO model: Methodical considerations and numerical results","volume":"14","year":"1993","journal-title":"J.\u00a0Comput. Chem."},{"key":"2026102008015511200_c17","doi-asserted-by":"publisher","first-page":"204107","DOI":"10.1063\/1.4806259","article-title":"SCC-DFTB calculation of the static first hyperpolarizability: From gas phase molecules to functionalized surfaces","volume":"138","year":"2013","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c18","doi-asserted-by":"publisher","first-page":"149","DOI":"10.1021\/jz402317x","article-title":"Origin of the surface-induced first hyperpolarizability in the C60\/SiO2 system: SCC-DFTB insight","volume":"5","year":"2014","journal-title":"J.\u00a0Phys. Chem. Lett."},{"key":"2026102008015511200_c19","doi-asserted-by":"publisher","first-page":"244104","DOI":"10.1063\/1.4811331","article-title":"A simplified Tamm-Dancoff density functional approach for the electronic excitation spectra of very large molecules","volume":"138","year":"2013","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c20","doi-asserted-by":"publisher","first-page":"45","DOI":"10.1016\/j.comptc.2014.02.023","article-title":"A simplified time-dependent density functional theory approach for electronic ultraviolet and circular dichroism spectra of very large molecules","volume":"1040\u20131041","year":"2014","journal-title":"Comput. Theor. Chem."},{"key":"2026102008015511200_c21","doi-asserted-by":"publisher","first-page":"054103","DOI":"10.1063\/1.4959605","article-title":"Ultra-fast computation of electronic spectra for large systems by tight-binding based simplified Tamm-Dancoff approximation (sTDA-xTB)","volume":"145","year":"2016","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c22","doi-asserted-by":"publisher","first-page":"184103","DOI":"10.1063\/1.4948647","article-title":"Tight-binding approximations to time-dependent density functional theory\u2014A fast approach for the calculation of electronically excited states","volume":"144","year":"2016","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c23","doi-asserted-by":"publisher","first-page":"084110","DOI":"10.1063\/5.0020545","article-title":"Minimal auxiliary basis set for time-dependent density functional theory and comparison with tight-binding approximations: Application to silver nanoparticles","volume":"153","year":"2020","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c24","doi-asserted-by":"publisher","first-page":"1968","DOI":"10.1021\/acs.jpclett.2c03698","article-title":"Minimal auxiliary basis set approach for the electronic excitation spectra of organic molecules","volume":"14","year":"2023","journal-title":"J.\u00a0Phys. Chem. Lett."},{"key":"2026102008015511200_c25","doi-asserted-by":"publisher","first-page":"4186","DOI":"10.1021\/acs.jctc.2c00144","article-title":"Excited-state properties for extended systems: Efficient hybrid density functional methods","volume":"18","year":"2022","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c26","doi-asserted-by":"publisher","first-page":"3438","DOI":"10.1021\/acs.jctc.2c00087","article-title":"Simplified GW\/BSE approach for charged and neutral excitation energies of large molecules and nanomaterials","volume":"18","year":"2022","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c27","doi-asserted-by":"publisher","first-page":"204111","DOI":"10.1063\/5.0071013","article-title":"Accelerating molecular property calculations with semiempirical preconditioning","volume":"155","year":"2021","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c28","doi-asserted-by":"publisher","first-page":"6738","DOI":"10.1021\/acs.jctc.4c00577","article-title":"Converging time-dependent density functional theory calculations in five iterations with minimal auxiliary preconditioning","volume":"20","year":"2024","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c29","doi-asserted-by":"publisher","first-page":"3841","DOI":"10.1021\/acs.jpca.1c02362","article-title":"Perspective on simplified quantum chemistry methods for excited states and response properties","volume":"125","year":"2021","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c30","doi-asserted-by":"publisher","first-page":"024108","DOI":"10.1063\/1.5037665","article-title":"Nonlinear-response properties in a simplified time-dependent density functional theory (sTD-DFT) framework: Evaluation of the first hyperpolarizability","volume":"149","year":"2018","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c31","doi-asserted-by":"publisher","first-page":"7534","DOI":"10.1021\/acs.jpca.2c02395","article-title":"Ultrafast evaluation of two-photon absorption with simplified time-dependent density functional theory","volume":"126","year":"2022","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c32","doi-asserted-by":"publisher","first-page":"094112","DOI":"10.1063\/1.5080199","article-title":"Nonlinear-response properties in a simplified time-dependent density functional theory (sTD-DFT) framework: Evaluation of excited-state absorption spectra","volume":"150","year":"2019","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c33","doi-asserted-by":"publisher","first-page":"084116","DOI":"10.1063\/5.0020543","article-title":"Simplified time-dependent density functional theory (sTD-DFT) for molecular optical rotation","volume":"153","year":"2020","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c34","doi-asserted-by":"publisher","first-page":"5815","DOI":"10.1021\/acs.jpca.9b03176","article-title":"A simplified spin-flip time-dependent density functional theory approach for the electronic excitation spectra of very large diradicals","volume":"123","year":"2019","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c35","doi-asserted-by":"publisher","first-page":"204110","DOI":"10.1063\/5.0206380","article-title":"The eXact integral simplified time-dependent density functional theory (XsTD-DFT)","volume":"160","year":"2024","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c36","doi-asserted-by":"publisher","first-page":"12628","DOI":"10.1021\/acs.jpclett.4c03193","article-title":"Computing excited states of very large systems with range-separated hybrid functionals and the exact integral simplified time-dependent density functional theory (XsTD-DFT)","volume":"15","year":"2024","journal-title":"J.\u00a0Phys. Chem. Lett."},{"key":"2026102008015511200_c37","article-title":"std2: A program for computing excited states and response functions via simplified TD-DFT methods (sTDA, sTD-DFT, SF-sTD-DFT, XsTDA, XsTD-DFT, and SF-Xs-TD-DFT)","year":"2025"},{"key":"2026102008015511200_c38","doi-asserted-by":"publisher","first-page":"e202401121","DOI":"10.1002\/cphc.202401121","article-title":"All-atom quantum mechanical methodologies for one- and two-photon absorption of realistic systems","volume":"26","year":"2025","journal-title":"ChemPhysChem"},{"key":"2026102008015511200_c39","doi-asserted-by":"publisher","first-page":"1280","DOI":"10.1103\/physrevlett.80.1280","article-title":"Causality and symmetry in time-dependent density-functional theory","volume":"80","year":"1998","journal-title":"Phys. Rev. Lett."},{"key":"2026102008015511200_c40","first-page":"155","article-title":"Time-dependent density functional response theory for molecules","volume-title":"Recent Advances in Density Functional Methods","year":"1995"},{"key":"2026102008015511200_c41","doi-asserted-by":"publisher","first-page":"807","DOI":"10.1021\/acs.jctc.7b01008","article-title":"Quadratic response properties from TDDFT: Trials and tribulations","volume":"14","year":"2018","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c42","doi-asserted-by":"publisher","first-page":"291","DOI":"10.1016\/s0009-2614(99)01149-5","article-title":"Time-dependent density functional theory within the Tamm-Dancoff approximation","volume":"314","year":"1999","journal-title":"Chem. Phys. Lett."},{"key":"2026102008015511200_c43","doi-asserted-by":"publisher","first-page":"1610","DOI":"10.1021\/ct100729t","article-title":"On the efficiency of algorithms for solving Hartree-Fock and Kohn-Sham response equations","volume":"7","year":"2011","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c44","doi-asserted-by":"publisher","first-page":"174105","DOI":"10.1063\/1.4947245","article-title":"Accelerating molecular property calculations with nonorthonormal Krylov space methods","volume":"144","year":"2016","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c45","doi-asserted-by":"publisher","first-page":"9684","DOI":"10.1021\/acs.jpclett.1c02911","article-title":"All-atom quantum mechanical calculation of the second-harmonic generation of fluorescent proteins","volume":"12","year":"2021","journal-title":"J.\u00a0Phys. Chem. Lett."},{"key":"2026102008015511200_c46","doi-asserted-by":"publisher","first-page":"25","DOI":"10.1016\/s0065-3276(08)60071-4","article-title":"Zero differential overlap in \u03d5-electron theories","volume":"2","year":"1966","journal-title":"Adv. Quantum Chem."},{"key":"2026102008015511200_c47","doi-asserted-by":"publisher","first-page":"389","DOI":"10.1007\/bf00526457","article-title":"Justifiability of the ZDO approximation in terms of a power series expansion","volume":"18","year":"1970","journal-title":"Theor. Chim. Acta"},{"key":"2026102008015511200_c48","doi-asserted-by":"publisher","first-page":"131","DOI":"10.1007\/bf00554120","article-title":"A re-examination of the justification of neglect of differential overlap approximations in terms of a power series expansion in S","volume":"54","year":"1980","journal-title":"Theor. Chim. Acta"},{"key":"2026102008015511200_c49","doi-asserted-by":"publisher","first-page":"4550","DOI":"10.1021\/ja01075a008","article-title":"A semiempirical treatment of molecular structures. II. Molecular terms and application to diatomic molecules","volume":"86","year":"1964","journal-title":"J.\u00a0Am. Chem. Soc."},{"key":"2026102008015511200_c50","doi-asserted-by":"publisher","first-page":"513","DOI":"10.1080\/00268977100100481","article-title":"Perturbation theory of the non-linear optical polarization of an isolated system","volume":"20","year":"1971","journal-title":"Mol. Phys."},{"key":"2026102008015511200_c51","doi-asserted-by":"publisher","first-page":"7709","DOI":"10.1021\/acs.jctc.0c00990","article-title":"A unified strategy for the chemically intuitive interpretation of molecular optical response properties","volume":"16","year":"2020","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c52","doi-asserted-by":"publisher","first-page":"9828","DOI":"10.1021\/acs.jpca.9b08474","article-title":"Are fully conjugated expanded indenofluorenes analogues and diindeno[n]thiophene derivatives diradicals? A simplified (spin-flip) time-dependent density functional theory [(SF-)sTD-DFT] study","volume":"123","year":"2019","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c53","doi-asserted-by":"publisher","first-page":"375","DOI":"10.1016\/s0009-2614(01)00287-1","article-title":"Size-consistent wave functions for bond-breaking: The equation-of-motion spin-flip model","volume":"338","year":"2001","journal-title":"Chem. Phys. Lett."},{"key":"2026102008015511200_c54","doi-asserted-by":"publisher","first-page":"1664","DOI":"10.1002\/jcc.23981","article-title":"Libcint: An efficient general integral library for Gaussian basis functions","volume":"36","year":"2015","journal-title":"J.\u00a0Comput. Chem."},{"key":"2026102008015511200_c55","doi-asserted-by":"publisher","first-page":"580","DOI":"10.1002\/jcc.22885","article-title":"Multiwfn: A multifunctional wavefunction analyzer","volume":"33","year":"2012","journal-title":"J.\u00a0Comput. Chem."},{"key":"2026102008015511200_c56","doi-asserted-by":"publisher","first-page":"23643","DOI":"10.1039\/d1cp03741b","article-title":"Self-assembling, structure and nonlinear optical properties of fluorescent organic nanoparticles in water","volume":"23","year":"2021","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026102008015511200_c57","article-title":"g-xTB: A general-purpose extended tight-binding electronic structure method for the elements H to Lr (Z = 1\u2013103)"},{"key":"2026102008015511200_c58","doi-asserted-by":"publisher","first-page":"14531","DOI":"10.1039\/c3cp55490b","article-title":"Optical spectrum, perceived color, refractive index, and non-adiabatic dynamics of the photochromic diarylethene CMTE","volume":"16","year":"2014","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026102008015511200_c59","doi-asserted-by":"publisher","first-page":"3653","DOI":"10.1021\/acs.jpca.5b01680","article-title":"Electronic circular dichroism of highly conjugated \u03c0-systems: Breakdown of the Tamm\u2013Dancoff\/configuration interaction singles approximation","volume":"119","year":"2015","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c60","doi-asserted-by":"publisher","first-page":"37","DOI":"10.1002\/cphc.201500626","article-title":"Differential many-body cooperativity in electronic spectra of oligonuclear transition-metal complexes","volume":"17","year":"2016","journal-title":"ChemPhysChem"},{"key":"2026102008015511200_c61","doi-asserted-by":"publisher","first-page":"7669","DOI":"10.1039\/c8dt00642c","article-title":"Bismuth as a versatile cation for luminescence in coordination polymers from BiX3\/4,4\u2032-bipy: Understanding of photophysics by quantum chemical calculations and structural parallels to lanthanides","volume":"47","year":"2018","journal-title":"Dalton Trans."},{"key":"2026102008015511200_c62","doi-asserted-by":"publisher","first-page":"365","DOI":"10.1002\/chir.22594","article-title":"Electronic circular dichroism of [16]helicene with simplified TD-DFT: Beyond the single structure approach","volume":"28","year":"2016","journal-title":"Chirality"},{"key":"2026102008015511200_c63","doi-asserted-by":"publisher","first-page":"1075","DOI":"10.1021\/acs.joc.5b02638","article-title":"Axial, helical, and planar chirality in directly linked basket-handle porphyrin arrays","volume":"81","year":"2016","journal-title":"J.\u00a0Org. Chem."},{"key":"2026102008015511200_c64","doi-asserted-by":"publisher","first-page":"2530","DOI":"10.1021\/acs.jnatprod.6b00395","article-title":"Atropoisomerism in biflavones: The absolute configuration of (\u2013)-agathisflavone via chiroptical spectroscopy","volume":"79","year":"2016","journal-title":"J.\u00a0Nat. Prod."},{"key":"2026102008015511200_c65","doi-asserted-by":"publisher","first-page":"7265","DOI":"10.1021\/acsomega.8b03500","article-title":"Methodological survey of simplified TD-DFT methods for fast and accurate interpretation of UV-Vis-NIR spectra of phthalocyanines","volume":"4","year":"2019","journal-title":"ACS Omega"},{"key":"2026102008015511200_c66","doi-asserted-by":"publisher","first-page":"11682","DOI":"10.1021\/jacs.7b05833","article-title":"Biomolecular structure information from high-speed quantum mechanical electronic spectra calculation","volume":"139","year":"2017","journal-title":"J.\u00a0Am. Chem. Soc."},{"key":"2026102008015511200_c67","doi-asserted-by":"publisher","first-page":"140","DOI":"10.1007\/s12539-020-00402-7","article-title":"Ultra-fast computation of excited-states spectra for large systems: Ultraviolet and fluorescence spectra of proteins","volume":"13","year":"2021","journal-title":"Interdiscip. Sci.: Comput. Life Sci."},{"key":"2026102008015511200_c68","doi-asserted-by":"publisher","first-page":"10955","DOI":"10.3390\/ijms231810955","article-title":"Semi-empirical calculation of bodipy aggregate spectroscopic properties through direct sampling of configurational ensembles","volume":"23","year":"2022","journal-title":"Int. J. Mol. Sci."},{"key":"2026102008015511200_c69","doi-asserted-by":"publisher","first-page":"2450","DOI":"10.1021\/acs.jcim.8b00256","article-title":"High-throughput screening approach for the optoelectronic properties of conjugated polymers","volume":"58","year":"2018","journal-title":"J.\u00a0Chem. Inf. Model."},{"key":"2026102008015511200_c70","doi-asserted-by":"publisher","first-page":"14","DOI":"10.1038\/s42004-020-0256-7","article-title":"Mapping the optoelectronic property space of small aromatic molecules","volume":"3","year":"2020","journal-title":"Commun. Chem."},{"key":"2026102008015511200_c71","doi-asserted-by":"publisher","first-page":"134116","DOI":"10.1063\/5.0084535","article-title":"Machine learned calibrations to high-throughput molecular excited state calculations","volume":"156","year":"2022","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c72","doi-asserted-by":"publisher","first-page":"8818","DOI":"10.1021\/acs.jpca.2c05253","article-title":"Theoretical investigation of the electronic spectra of cadmium chalcogenide 2D nanoplatelets","volume":"126","year":"2022","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c73","article-title":"Simplified time-dependent density-functional theory for noble metal nanoclusters: Progress toward the Tamm\u2013Dancoff approximation","year":"2026"},{"key":"2026102008015511200_c74","doi-asserted-by":"publisher","first-page":"8178","DOI":"10.1021\/acs.jpca.5c03189","article-title":"Evaluating the performance of the exact integral simplified time-dependent density functional theory (XsTD-DFT) to compute one- and two-photon absorption","volume":"129","year":"2025","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c75","doi-asserted-by":"publisher","first-page":"202","DOI":"10.1007\/s00894-026-06774-9","article-title":"Singlet fission tinkertoys based on N-heterocyclic carbenes: The role of stereoisomerism","volume":"32","year":"2026","journal-title":"J.\u00a0Mol. Model."},{"key":"2026102008015511200_c76","doi-asserted-by":"publisher","first-page":"13132","DOI":"10.1021\/acs.jpclett.5c03411","article-title":"Ultrafast near-edge X-ray absorption fine structure calculations with the exact integral simplified time-dependent density functional theory (XsTD-DFT) for large systems","volume":"16","year":"2025","journal-title":"J.\u00a0Phys. Chem. Lett."},{"key":"2026102008015511200_c77","doi-asserted-by":"publisher","first-page":"2594","DOI":"10.1080\/00268976.2018.1524525","article-title":"Photoinduced flavin-tryptophan electron transfer across vesicle membranes generates magnetic field sensitive radical pairs","volume":"117","year":"2019","journal-title":"Mol. Phys."},{"key":"2026102008015511200_c78","doi-asserted-by":"publisher","first-page":"9950","DOI":"10.1039\/c3cp54470b","article-title":"Effect of chromophore encapsulation on linear and nonlinear optical properties: The case of \u2018miniSOG,\u2019 a protein-encased flavin","volume":"16","year":"2014","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026102008015511200_c79","doi-asserted-by":"publisher","first-page":"7002","DOI":"10.1021\/acs.jctc.4c01788","article-title":"An efficient exciton coupling scheme based on simplified time-dependent density functional theory","volume":"21","year":"2025","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c80","doi-asserted-by":"publisher","first-page":"10930","DOI":"10.1021\/jp2055409","article-title":"Optical rotation calculated with time-dependent density functional theory: The OR45 benchmark","volume":"115","year":"2011","journal-title":"J.\u00a0Phys. Chem. A"},{"key":"2026102008015511200_c81","doi-asserted-by":"publisher","first-page":"319","DOI":"10.1016\/j.cplett.2004.06.065","article-title":"Origin invariant calculation of optical rotation without recourse to London orbitals","volume":"393","year":"2004","journal-title":"Chem. Phys. Lett."},{"key":"2026102008015511200_c82","doi-asserted-by":"publisher","first-page":"151101","DOI":"10.1063\/5.0028849","article-title":"Origin invariant optical rotation in the length dipole gauge without London atomic orbitals","volume":"153","year":"2020","journal-title":"J.\u00a0Chem. Phys."},{"key":"2026102008015511200_c83","doi-asserted-by":"publisher","first-page":"6909","DOI":"10.1021\/acs.jpcc.7b00625","article-title":"Fluorescence-free spectral dispersion of the molecular first hyperpolarizability of bacteriorhodopsin","volume":"121","year":"2017","journal-title":"J.\u00a0Phys. Chem. C"},{"key":"2026102008015511200_c84","doi-asserted-by":"publisher","first-page":"2449","DOI":"10.1021\/ct500114m","article-title":"Efficient calculations of molecular linear response properties for spectral regions","volume":"10","year":"2014","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c85","doi-asserted-by":"publisher","first-page":"16949","DOI":"10.1039\/c8cp01699b","article-title":"Two photon spectroscopy and microscopy of the fluorescent flavoprotein, iLOV","volume":"20","year":"2018","journal-title":"Phys. Chem. Chem. Phys."},{"key":"2026102008015511200_c86","doi-asserted-by":"publisher","first-page":"2568","DOI":"10.1021\/acs.jpcb.0c00643","article-title":"Dynamic structural effects on the second-harmonic generation of tryptophane-rich peptides and gramicidin A","volume":"124","year":"2020","journal-title":"J.\u00a0Phys. Chem. B"},{"key":"2026102008015511200_c87","doi-asserted-by":"publisher","first-page":"e70336","DOI":"10.1002\/jcc.70336","article-title":"Simplified time-dependent DFT for all-atom simulations of second harmonic generation responses: A case study on photoswitchable azobenzene monolayers","volume":"47","year":"2026","journal-title":"J.\u00a0Comput. Chem."},{"key":"2026102008015511200_c88","doi-asserted-by":"publisher","first-page":"2777","DOI":"10.1021\/ct300307c","article-title":"Analysis of excitonic and charge transfer interactions from quantum chemical calculations","volume":"8","year":"2012","journal-title":"J.\u00a0Chem. Theory Comput."},{"key":"2026102008015511200_c89","article-title":"Drastically reducing the cost of the XsTD-DFT family of methods using a minimal auxiliary basis set (\u03b7XsTD-DFT) to efficiently treat ultra large systems","year":"2026","journal-title":"Phys. Chem. Chem. Phys."}],"container-title":["The Journal of Chemical Physics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.aip.org\/aip\/jcp\/article-pdf\/doi\/10.1063\/5.0349975\/21175264\/152501_1_5.0349975.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.aip.org\/aip\/jcp\/article-pdf\/doi\/10.1063\/5.0349975\/21175264\/152501_1_5.0349975.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T12:02:05Z","timestamp":1792497725000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.aip.org\/jcp\/article\/165\/15\/152501\/3406839\/The-std2-package-A-computationally-efficient"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,20]]},"references-count":89,"journal-issue":{"issue":"15","published-print":{"date-parts":[[2026,10,21]]}},"URL":"https:\/\/doi.org\/10.1063\/5.0349975","relation":{},"ISSN":["0021-9606","1089-7690"],"issn-type":[{"value":"0021-9606","type":"print"},{"value":"1089-7690","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2026,10,21]]},"published":{"date-parts":[[2026,10,20]]},"article-number":"152501"}}