Download Stat Mech

َ ‫ هُمام‬.‫ د‬.‫أ‬
‫غص ٍييب‬
Prof. Dr. Humam B. Ghassib
STATISTICAL MECHANICS –1
(0342756)
Preamble ‫تمهيد‬
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1. Statistical Mechanics is that branch of theoretical physics
which seeks to draw a connection between the macroscopic
viewpoint of matter and its microscopic constitution. The
behavior of bulk macroscopic matter is described in such
thermodynamic terms as volume, density, pressure and
temperature – none of which is meaningful when applied
to single atoms or molecules. Yet, bulk laboratory matter
does consist entirely of atoms and molecules. The
instantaneous states of these elementary constituents are
described classically by their positions and velocities (or
momenta); and the motions are governed by the laws of
mechanics. The task of Statistical Mechanics is, then, to
infer the behavior of bulk matter (i.e., the macroscopic
system) from a knowledge of the structure of the particles
composing it, using the laws of mechanics. The use of
quantum, rather than classical, mechanics does not seriously
affect this fundamental task.
It merely alters the
‘mechanical’ description of the constituent particles –
precise assessments of position and velocity being replaced
with probability distributions or wave functions.
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2. The scope of Statistical Mechanics is almost as wide as the
very range of natural phenomena.
In fact, it has been
applied, with considerable success, to the study of matter in
the solid, liquid and gaseous states; matter in the ‘fourth
state’,
i.e., plasma; matter composed of several phases
and/or several
components; matter under extreme
conditions of density and temperature [sometimes called the
‘fifth state’]
(in astrophysics, for example); matter in
equilibrium with radiation; living matter, i.e., matter in the
form of a biological specimen; soft condensed matter, e.g.,
suspensions, emulsions and foams, liquid crystals, polymers,
and membranes;
and so forth.
Moreover, Statistical
Mechanics is suitable for investigating equilibrium, as well
as nonequilibrium, states of matter.
3. However, in this course, we shall concentrate almost
exclusively on the equilibrium state (in which the system
undergoes no macroscopically-observable changes in a
given interval of time). Our aim is twofold: first, to study
thoroughly the theoretical principles involved; and, second,
to consider some applications.
Prof. Dr. Humam Ghassib
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