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{{Infobox software
| name = Leiden Classical
| screenshot = Leiden.gif
| caption = Leiden Classical screensaver graphics
| description = Leiden Classical is a completed volunteer computing BOINC project run by the Theoretical Chemistry Department of the Leiden Institute of Chemistry at Leiden University, allowing scientists and students to submit personal classical mechanics and molecular dynamics simulations to a volunteer grid.

| status = Completed
| category = Chemistry, Physics
| compute = CPU
| dependencies =

| developer = Theoretical Chemistry Department, Leiden Institute of Chemistry
| sponsor = [[wikipedia:Leiden University|Leiden University]]
| maintainer = Theoretical Chemistry Department, Leiden Institute of Chemistry
| released = {{Start date and age|2005|12|05}}
| completed = {{Start date and age|2018|06|05}}
| discontinued =
| repository =

| programming language = C++
| operating system = Windows, Linux
| size =

| website = {{URL|http://boinc.gorlaeus.net/}}
| license = GPL (main program), LGPL (ClassicalDynamics library)
}}

'''Leiden Classical''' is a completed [[wikipedia:volunteer computing|Volunteer computing]] project that ran on the [[wikipedia:Berkeley_Open_Infrastructure_for_Network_Computing|BOINC]] platform, operated by the Theoretical Chemistry Department of the Leiden Institute of Chemistry at [[wikipedia:Leiden University|Leiden University]] in the Netherlands.<ref name="wikipedia">{{cite web |title=Leiden Classical |url=https://en.wikipedia.org/wiki/Leiden_Classical |website=Wikipedia |access-date=2026-06-22}}</ref> Unlike most BOINC projects, which distribute a single fixed scientific workload to volunteers, Leiden Classical was built around ''user-submitted'' simulations: any scientist, student, or volunteer could design and submit their own classical-mechanics simulation to be computed on the grid, with each participant receiving a personal job queue.<ref name="boincwiki">{{cite web |title=Leiden Classical |url=https://boinc.berkeley.edu/wiki/Leiden_Classical |website=BOINC Wiki |publisher=University of California, Berkeley |access-date=2026-06-22}}</ref>

The project officially launched on 5 December 2005<ref name="projectlist">{{cite web |title=Project list |url=https://boinc.berkeley.edu/wiki/project_list |website=BOINC Wiki |publisher=University of California, Berkeley |access-date=2026-06-22}}</ref> and operated for nearly thirteen years before being formally retired on 5 June 2018.<ref name="endofops">{{cite web |title=Leiden Classical - End of Operations notice |url=https://boinc.berkeley.edu/forum_thread.php?id=12505 |website=BOINC Message Boards |publisher=University of California, Berkeley |date=2018-06-26 |access-date=2026-06-22}}</ref>

== Overview ==

Leiden Classical's tagline described it as a "Desktop Computer Grid dedicated to general Classical Dynamics for any scientist or science student."<ref name="sully">{{cite web |title=Leiden Classical project details |url=https://tsbt.co.uk/forum/viewtopic.php?t=2003 |website=The Scottish Boinc Team |access-date=2026-06-22}}</ref> Its core software, '''ClassicalDynamics''', was a simulation engine and accompanying library written entirely in [[wikipedia:C++|C++]].<ref name="wikipedia"/> The ClassicalDynamics library itself was released under the [[wikipedia:GNU Lesser General Public License|GNU Lesser General Public License]] (LGPL), while the main driving program was released under the [[wikipedia:GNU General Public License|GNU General Public License]] (GPL).<ref name="wikipedia"/><ref name="archived_license">{{cite web |title=Archived copy of Classical.txt |url=https://web.archive.org/web/20180619130038/http://boinc.gorlaeus.net/download/DownLoads/Classical.txt |website=Wayback Machine |archive-date=2018-06-19 |access-date=2026-06-22}}</ref>

The project's official description framed its purpose as performing "surface science calculations using Classical Dynamics," distinguishing it from most other BOINC projects by allowing volunteers, students, and other scientists to submit their own personal calculations directly to the grid.<ref name="projectlist"/><ref name="boincwiki"/> Two of the most commonly cited example use cases were simulating liquid [[wikipedia:Argon|argon]], and testing the validity of the [[wikipedia:Ideal gas law|ideal gas law]] by direct simulation rather than theoretical derivation.<ref name="boincwiki"/>

The project ran on Windows and Linux clients and did not support GPU computation or an OpenGL screensaver.<ref name="mundayweb">{{cite web |title=Leiden Classical |url=https://boinc.mundayweb.com/wiki/index.php?title=Leiden_Classical |website=BOINC Wiki (mundayweb mirror) |access-date=2026-06-22}}</ref>

== Simulation model ==

To submit a personal calculation, a participant's model required six defined components:<ref name="wikipedia"/>

* The colours used to represent the molecules in the simulation
* The bounding box in which the model was run
* The number of particles included in the simulation
* The type of interaction between particles, selectable from:
** [[wikipedia:Gravity|Gravity]]
** [[wikipedia:Coulomb's law|Coulomb force]]
** [[wikipedia:Lennard-Jones potential|Lennard-Jones interaction]]
** [[wikipedia:Morse potential|Morse interaction]]
** [[wikipedia:Rydberg state|Rydberg interaction]]
* Harmonic spring and harmonic bending terms, along with recurrent torsion interactions
* Distance and confirmation (boundary/constraint) parameters

The Lennard-Jones potential, one of the selectable pairwise interaction models, is given by:

<math>V_{LJ}(r) = 4\varepsilon \left[ \left( \frac{\sigma}{r} \right)^{12} - \left( \frac{\sigma}{r} \right)^{6} \right]</math>

where <math>r</math> is the distance between two particles, <math>\varepsilon</math> is the depth of the potential well, and <math>\sigma</math> is the finite distance at which the inter-particle potential is zero.

The Morse interaction, an alternative pairwise model better suited to representing covalent bond vibration, is given by:

<math>V_{M}(r) = D_e \left( 1 - e^{-a(r - r_e)} \right)^2</math>

where <math>D_e</math> is the well depth, <math>r_e</math> is the equilibrium bond distance, and <math>a</math> controls the width of the potential well.

This flexible, user-configurable approach allowed the grid to be applied to a range of small-scale classical and surface-science problems chosen by individual users rather than a single fixed research question, which was unusual among BOINC-based projects at the time.<ref name="projectlist"/>

== History ==

Leiden Classical was launched on 5 December 2005 by Leiden University,<ref name="projectlist"/> based in the city of [[wikipedia:Leiden|Leiden]] in the Netherlands. The project remained active for over a decade, continuing to accept volunteer participation through the BOINC manager client throughout this period.<ref name="wikipedia"/>

In its final news update, posted to the project's own news feed and referenced in community discussion, the project announced it had reached end-of-life status: automatic work generation and account creation were stopped, with the server scheduled to be taken offline before the end of 2018.<ref name="tsbt_endoflife">{{cite web |title=Leiden Project has ended |url=https://www.tsbt.co.uk/forum/viewtopic.php?t=9584 |website=The Scottish Boinc Team |date=2018-05-10 |access-date=2026-06-22}}</ref>

On 5 June 2018, the project posted its final operational notice, stating that "the scheduler, file uploader and all other daemons have been stopped" and that the website would "stay online for some time still."<ref name="endofops"/> The announcement was relayed to the wider BOINC community via the official BOINC project forums later that month.<ref name="endofops"/>

== Reception ==

Leiden Classical retained a small, dedicated base of volunteers across various national and team-based BOINC communities throughout its operation, including teams from Scotland, Catalonia, Australia, and Germany.<ref name="sully"/><ref name="boinccat">{{cite web |title=Leiden Classical |url=http://boinc.cat/content/leiden-classical |website=Comunitat catalana de càlcul distribuït |access-date=2026-06-22}}</ref><ref name="forumau">{{cite web |title=Leiden Classical |url=https://forum.boinc-australia.net/index.php?board=31.0 |website=BOINC@AUSTRALIA Forum |access-date=2026-06-22}}</ref><ref name="rechenkraft">{{cite web |title=Leiden Classical/Verbindung getrennt |url=https://www.rechenkraft.net/forum/viewtopic.php?p=79705 |website=Rechenkraft.net e.V. |access-date=2026-06-22}}</ref> When the shutdown was announced on the Scottish Boinc Team forums, one volunteer who lived in Leiden described themselves as "devastated," while another recalled having cycled through the city.<ref name="tsbt_endoflife"/>

== See also ==

* [[BOINC]]
* [[Einstein@Home]]
* [[wikipedia:Volunteer computing|Volunteer computing]]
* [[wikipedia:Leiden University|Leiden University]]
* [[wikipedia:Classical mechanics|Classical mechanics]]
* [https://boinc.berkeley.edu/pubs.php Publications by BOINC Projects]

== References ==

{{Reflist}}

[[Category:BOINC projects]]
[[Category:Completed projects]]
[[Category:Chemistry projects]]
[[Category:Physics projects]]

Leiden Classical - Revision history

Al Piskun: first light