Adventures in Computational Chemistry

An Ensemble provides the physical description of the system. A system can be completely described interms of the three components of the velocity and position each for every atom in the system. But, this is an almost impossible information to collect. Instead, while describing a system, people use measurable average properties like energy, pressure etc. These properties do not depend on the individual characterization of each constituting atom of the system. But, at the same time these properties also do not characterize the system completely. One set of values of these properties may correspond to different states of the system. Based only on one set of properties thus, it is thus difficult to pinpoint at a particular state of the system. So every possible state of a system has equal probability corresponding to a value of measurable average property . At a given time, the system can be in only one state. If the same system with one set of properties is considered exisiting at dif