CHAPTER 4
Quantum Effects
at the Nanoscale
During our study of thermodynamics and kinetics in the last two chapters,
we described the properties of bulk and nanoscale systems as state or
path functions that could have any physically meaningful value (e.g., any
nonnegative value for total energy or entropy, or any real value for
changes in energy). Such a description is based in classical physics, a
group of theories that had been developed by the end of the nineteenth
century. Most of what you learned in general physics was classical
physics, and to this day, classical physics provides an effective system for
characterizing many bulk materials and processes as well as systems
containing large numbers of particles. However, classical physics was
unable to explain a number of the key aspects of the interaction between
light and matter, leading to the discovery in the early twenthieth century
by Planck and Einstein that energy is quantized, meaning that the energy
of a system has a number of discrete possible values. This led to the
development of the field of quantum mechanics.
For a system that contains a large number of particles and/or has sufficient energy to access many states, the possible energies for the system
appear continuous, and classical physics remains a good approximation.
This is why, for example, we can represent the Gibbs energy of formation
for silver nanoparticles from solution using classical physics—many
particles are present. However, at the nanoscale, classical physics is no
longer able to accurately represent individual particles, and we must
account for quantum effects as well.
Quantum Effects
at the Nanoscale
During our study of thermodynamics and kinetics in the last two chapters,
we described the properties of bulk and nanoscale systems as state or
path functions that could have any physically meaningful value (e.g., any
nonnegative value for total energy or entropy, or any real value for
changes in energy). Such a description is based in classical physics, a
group of theories that had been developed by the end of the nineteenth
century. Most of what you learned in general physics was classical
physics, and to this day, classical physics provides an effective system for
characterizing many bulk materials and processes as well as systems
containing large numbers of particles. However, classical physics was
unable to explain a number of the key aspects of the interaction between
light and matter, leading to the discovery in the early twenthieth century
by Planck and Einstein that energy is quantized, meaning that the energy
of a system has a number of discrete possible values. This led to the
development of the field of quantum mechanics.
For a system that contains a large number of particles and/or has sufficient energy to access many states, the possible energies for the system
appear continuous, and classical physics remains a good approximation.
This is why, for example, we can represent the Gibbs energy of formation
for silver nanoparticles from solution using classical physics—many
particles are present. However, at the nanoscale, classical physics is no
longer able to accurately represent individual particles, and we must
account for quantum effects as well.