eprintid: 1474699 rev_number: 22 eprint_status: archive userid: 608 dir: disk0/01/47/46/99 datestamp: 2016-03-07 11:30:02 lastmod: 2021-10-04 00:42:55 status_changed: 2016-03-07 11:30:02 type: article metadata_visibility: show creators_name: O'Rourke, C creators_name: Bowler, DR title: Linear scaling density matrix real time TDDFT: Propagator unitarity and matrix truncation ispublished: pub divisions: UCL divisions: B04 divisions: C06 divisions: F60 note: © 2015 AIP Publishing LLC abstract: Real time, density matrix based, time dependent density functional theory (TDDFT) proceeds through the propagation of the density matrix, as opposed to the Kohn-Sham orbitals. It is possible to reduce the computational workload by imposing spatial cutoff radii on sparse matrices, and the propagation of the density matrix in this manner provides direct access to the optical response of very large systems, which would be otherwise impractical to obtain using the standard formulations of TDDFT. Following a brief summary of our implementation, along with several benchmark tests illustrating the validity of the method, we present an exploration of the factors affecting the accuracy of the approach. In particular, we investigate the effect of basis set size and matrix truncation, the key approximation used in achieving linear scaling, on the propagator unitarity and optical spectra. Finally, we illustrate that, with an appropriate density matrix truncation range applied, the computational load scales linearly with the system size and discuss the limitations of the approach. date: 2015-09-14 date_type: published official_url: http://dx.doi.org/10.1063/1.4919128 oa_status: green full_text_type: pub language: eng primo: open primo_central: open_green article_type_text: Journal Article verified: verified_manual elements_id: 1059060 doi: 10.1063/1.4919128 language_elements: eng lyricists_name: Bowler, David lyricists_id: DBOWL76 actors_name: Bowler, David actors_id: DBOWL76 actors_role: owner full_text_status: public publication: Journal of Chemical Physics volume: 143 number: 10 article_number: 102801 event_location: United States issn: 1089-7690 citation: O'Rourke, C; Bowler, DR; (2015) Linear scaling density matrix real time TDDFT: Propagator unitarity and matrix truncation. Journal of Chemical Physics , 143 (10) , Article 102801. 10.1063/1.4919128 <https://doi.org/10.1063/1.4919128>. Green open access document_url: https://discovery.ucl.ac.uk/id/eprint/1474699/1/O%E2%80%99Rourke%2C%20Bowler%20-%202015%20-%20Linear%20scaling%20density%20matrix%20real%20time%20TDDFT%20Propagator%20unitarity%20and%20matrix%20truncation.pdf