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# ORCA 6.1 Foreword
```{index} Foreword by F. Neese
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It was less than one year ago, July 2024, that ORCA 6.0 was released to
the general public by a proud and happy but also thoroughly exhausted
development team.
As we pointed out at the time, ORCA 6.0 was less an update to an existing program
but rather a completely re-imagined quantum chemistry program suite in which large
parts of the massive code base where re-designed and rewritten from scratch.
This process took nearly three years and resulted in a program
that was much leaner, much cleaner and as a result also more modern and
more efficient.

Our promise at the time of the release of ORCA 6.0 was that the new
infrastructure would allow for much more rapid and more confident method
development than ever before. With the release of ORCA 6.1, we believe
that we made good on this promise. Despite less than one year has passed
since the release of ORCA 6.0, version 6.1 is packed with new features
and further significant improvements under the hood. This release can
therefore indeed be regarded as a proof-of-principle for the new
infrastructure. It turned out to be so encouraging that we have every
intention to keep up the pace and aim at a release of a new ORCA version
approximately every 12 months -- hold us to it!

ORCA 6.1 is the result of the work of many individuals. The bulk of the
work has been done by the development teams at the Max Planck institute
für Kohlenforschung in Mülheim an der Ruhr, Germany and at FACCTs in
Cologne, Germany. However, we also very much enjoy our increasingly
numerous collaborations with other research groups around the world -
thank you so much, you rock!

I want to express my gratitude to all the many people who have put their
enthusiasm and hard work into making this release reality. All of them
were, are and will continue to be instrumental for the success of what
now has become a very large project! An ORCA release would not be
possible without the ORCA development team, led by Frank Wennmohs and
featuring Ute Becker, Dagmar Lenk, Dimitrios Liakos, Kantharuban
Sivalingam and Axel Koslowski, who have done invaluable work in making
sure that the code stays healthy, our libraries are up to date, that it
compiles on all platforms (*and* give correct results
everywhere), educate the developers on good programming style, fixing
countless bugs, parallelizing everything and going after each and every
deviation that our massive test suite reports.

Alexander Auer and Markus Bursch have taken the lead on
the important but incredibly tedious task to restructure the mammoth
that the ORCA manual has become, making sure that it is up to date and
available in HTML and PDF versions. Thank you so much! The importance of
that work cannot possibly be overemphasized.

It gives me enormous pleasure to observe the increasing impact on
industrial computational chemistry that FACCTs has under the outstanding
leadership of Christoph Riplinger. This not only leads to rapid and
sustainable growth of the company but also provides many important ideas
and incentives for exciting science. The development team at FACCTs
continues to make many important contributions to the code, exciting new
features, new methods, new workflows together with an unwavering
commitment to precision and excellence. I should specifically mention
Bernardo de Souza, Georgi Stoychev, Miquel Garcia-Rates, Ingolf
Harden, Nicolas Foglia
and Hagen Neugebauer. Thank you all -- it is a pleasure!

Working on an ORCA release is not a chore, it is a labour of passion,
joy and dedication. It gives me incredible joy to work on something that
proves to be useful for tens of thousands of people all around the
globe. It also gives me incredible joy to work on this as part of a team
that is enthusiastic, highly motivated, highly skilled and highly
dedicated.

Now you, the ORCA community, holds the next chapter of our journey in your hands.
We are proud of ORCA 6.1 and we promise that
this won't be our last rodeo in the continuing ORCA development. We hope
that you enjoy it as much as we enjoyed working on it - and - of course,
we hope that it helps you solving chemical problems, large or small,
whatever your scientific pathway may be.

Frank Neese

On behalf of the ORCA development team

May 26$^{th}$, 2025