## General Information

Boltzmann 3D is named for Austrian physicist Ludwig Boltzmann, who developed much of the theory of entropy and statistical mechanics. The Boltzmann distribution for energy and the Maxwell-Boltzmann distribution for velocity likewise carry his name. He also invented a now-famous and common equation to describe the approach of a system to equilibrium. Today, however, Boltzmann is best known for his definition of entropy in terms of the logarithm of the number of microstates. This equation (S = klnW; S= = entropy, k = proportionality constant, and W = number of microstates) is carved on his tomb. K, called Boltzmann's constant, may be multiplied with Avogadro's number to reach the universal gas constant, R. Thus Boltzmann's constant is the gas constant per molecule. Thus is Boltzmann immortalized in the history of the human understanding of chemistry.

Boltzmann 3D deals with visual illustrations of Boltzmann-like problems. Boltzmann 3D may be used as a classroom demonstrator of molecular motion if the program is run on a computer linked to a classroom projector. Boltzmann 3D may also be used as a hands-on activity for students trying to understand how molecular motion leads to macroscopic properties like chemical reaction rates, gas pressure, vapor pressure, diffusion, effusion, thermal transport, and more. (Suggestions for more uses are included in the documentation below.)

## History

In 1994 — long before Boltzmann 3D was written — Dr. Randall B. Shirts of the BYU Chemistry Department produced a two-dimensional program called MotionBYU to help BYU chemistry and physics students visualize the distribution of molecular velocities. MotionBYU was programmed in TurboPascal by David L. Summers (a then-undergraduate electrical engineering student). At the time, MotionBYU was likely the first program to perform real-time particle motion simulation, especially since the program was written on recently produced Intel 486 computers that made such simulations possible.

Summers later translated MotionBYU into C++ a Windows program. The program was rechristened by Boltzmann before being commercialized and distributed by Trinity Software. Eventually, the current iteration of Boltzmann, Boltzmann 3D, was written by Scott R. Burt (a current BYU faculty member who was an undergraduate when he wrote Boltzmann 3D) and Benjamin J. Lemmon (a then-undergraduate computer science major). The update was released in 2004. Boltzmann 3D outstrips earlier models in that it is programmed in Java using OpenGL graphics libraries, meaning Boltzmann 3D may be used on other platforms than Windows, includes 1D and 3D simulations, and features an improved user interface. BYU's Center for Teaching and Learning