Molecular dynamics at a constant pH

The dynamic equilibrium that exists in a chemically reacting system can be simulated using classical me chanics if the appropriate statistical mechanical ensem ble is chosen. This paper describes a general method that makes it possible to simulate this equilibrium in a simple chemical reaction through the use of a recently developed grand canonical molecular dynamics method. After a brief description of the method, an example calculation is performed that simulates the acid-base equilibrium between acetic acid and water. The computational demands of this application are discussed along with a description of a new MPP algo rithmic approach to this application.