However, given the very rapidly growing demand from industry, the company FAccTs was founded (Dr. From the start, ORCA has been freely available for academic researchers, a feature that we always considered as essential and non-negotiable. 1 ), ORCA has grown to be one of the most used quantum chemistry programs worldwide with more than 22 000 registered users (January 2020) 1 1. The electronic structure package ORCA has been developed since the late 1990’s mostly in the group of the authors but with important contributions from highly esteemed collaborators around the world. Consequently, ORCA is a widely used program in various areas of chemistry and spectroscopy with a current user base of over 22 000 registered users in academic research and in industry. Next to a range of spectroscopic and magnetic properties, the linear- or low-order single- and multi-reference local correlation methods based on pair natural orbitals (domain based local pair natural orbital methods) should be mentioned here. In addition to being efficient, user friendly, and, to the largest extent possible, platform independent, ORCA features a number of methods that are either unique to ORCA or have been first implemented in the course of the ORCA development. A specialty of ORCA always has been a focus on transition metals and spectroscopy as well as a focus on applicability of the implemented methods to “real-life” chemical applications involving systems with a few hundred atoms. A range of solvation and embedding models is featured as well as a complete intrinsic to ORCA quantum mechanics/molecular mechanics engine. ORCA features density functional theory, a range of wavefunction based correlation methods, semi-empirical methods, and even force-field methods. ORCA has grown into a rather comprehensive general-purpose package for theoretical research in all areas of chemistry and many neighboring disciplines such as materials sciences and biochemistry. We start with a short historical perspective of how the project began and go on to discuss its current feature set. In this contribution to the special software-centered issue, the ORCA program package is described. Jagau, Yousung Jung, Andreas Klamt, Jing Kong, Daniel S. Goddard, Sharon Hammes-Schiffer, Teresa Head-Gordon, Warren J. Brooks, David Casanova, Jeng-Da Chai, Sonia Coriani, Christopher J. Yost, Alexander Zech, Igor Ying Zhang, Xing Zhang, Yu Zhang, Dmitry Zuev, Alán Aspuru-Guzik, Alexis T. Tubman, Srimukh Prasad Veccham, Oleg Vydrov, Jan Wenzel, Jon Witte, Atsushi Yamada, Kun Yao, Sina Yeganeh, Shane R. Sundstrom, Zhen Tao, Jonathan Thirman, Gábor J. Sharada, Wojciech Skomorowski, David W. Richard, Fazle Rob, Elliot Rossomme, Tarek Scheele, Maximilian Scheurer, Matthias Schneider, Nickolai Sergueev, Shaama M. Proynov, Ádám Rák, Eloy Ramos-Cordoba, Bhaskar Rana, Alan E. Paul, Fabijan Pavošević, Zheng Pei, Stefan Prager, Emil I. Oosterbaan, Garrette Paran, Alexander C. Marenich, Thomas Markovich, Stephen Mason, Simon A. Li, Yi-Pei Li, Jiashu Liang, Marcus Liebenthal, Hung-Hsuan Lin, You-Sheng Lin, Fenglai Liu, Kuan-Yu Liu, Matthias Loipersberger, Arne Luenser, Aaditya Manjanath, Prashant Manohar, Erum Mansoor, Sam F. Lawler, Daniel Lefrancois, Susi Lehtola, Run R. Krauter, Karl Kue, Alexander Kunitsa, Thomas Kus, István Ladjánszki, Arie Landau, Keith V. Huynh, Maxim Ivanov, Ádám Jász, Hyunjun Ji, Hanjie Jiang, Benjamin Kaduk, Sven Kähler, Kirill Khistyaev, Jaehoon Kim, Gergely Kis, Phil Klunzinger, Zsuzsanna Koczor-Benda, Joong Hoon Koh, Dimitri Kosenkov, Laura Koulias, Tim Kowalczyk, Caroline M. Holden, Shannon Houck, Xunkun Huang, Kerwin Hui, Bang C. Herbst, Mario Hernández Vera, Manuel Hodecker, Zachary C. González-Espinoza, Sahil Gulania, Anastasia O. Closser, Vale Cofer-Shabica, Saswata Dasgupta, Marc de Wergifosse, Jia Deng, Michael Diedenhofen, Hainam Do, Sebastian Ehlert, Po-Tung Fang, Shervin Fatehi, Qingguo Feng, Triet Friedhoff, James Gayvert, Qinghui Ge, Gergely Gidofalvi, Matthew Goldey, Joe Gomes, Cristina E. Burton, Abel Carreras, Kevin Carter-Fenk, Romit Chakraborty, Alan D. Andersen, Vishikh Athavale, Dennis Barton, Khadiza Begam, Andrew Behn, Nicole Bellonzi, Yves A. Albrecht, Abdulrahman Aldossary, Ethan Alguire, Josefine H. Vidal, Zhi-Qiang You, Ying Zhu, Bushra Alam, Benjamin J. Jacobson, Ilya Kaliman, Jörg Kussmann, Adrian W. Dempwolff, Zhengting Gan, Diptarka Hait, Paul R. Gilbert, Xintian Feng, Joonho Lee, Yuezhi Mao, Narbe Mardirossian, Pavel Pokhilko, Alec F.

Chemistry calculator program