from traditional optical crystallographers since the well-defined spots and their
regular disposition on the photographic plate were seen as conclusive evidence
that atoms are arranged regularly in a space-lattice configuration in crystals and
suggested the possibility of atomic resolution. As Alfred Tutton, the English crystallographer, overstated in November 1912, “the space-lattice structure of crystals
. . . is now rendered visible to our eyes” [21]. Within a year of the discovery of X-ray
diffraction, William Lawrence Bragg had reinterpreted the phenomenon responsible
for the diffraction pattern and determined the first unit cell dimensions of simple
salts, and within 2 years he and his father (William Henry Bragg) had reported the
first crystal structure determinations [19, 20, 23, 24]. The discoveries of von Laue
and Bragg gave birth to two new sciences, X-ray crystallography and X-ray spectroscopy, and two Nobel Prizes: Max von Laue “for his discovery of the diffraction
of X-rays by crystals” in 1914 and to the Braggs “for their services in the analysis of
crystal structure by X-ray Crystallography in 1915 (see Table 1).
Von Laue’s experiment had confirmed unambiguously the wave nature of X-rays
and suggested that the wavelength was sufficiently short that it gave rise to a
diffraction pattern from the target crystal. However, he did not completely or
succinctly articulate the physics which was responsible for the phenomenon. He
argued that the internal order of atoms within the crystal, which had been hinted at
for several centuries, results in a three-dimensional diffraction grating with spacings
much smaller than that commonly associated with visible light and their exposure to
X-rays resulted in the observed diffraction pattern. Specifically, the lack of knowledge concerning the nature of the lattice and the wavelength(s) of the X-rays limited
his contribution. Nonetheless, this seed of an idea rapidly grew and blossomed, and
it was able to draw on the circumstantial evidence which had been obtained
previously from optical crystallography which had been developed initially to
study mineralogical samples but was also used to study inorganic crystals made by
chemists in the nineteenth century. This cross fertilisation is discussed in more detail
in the subsequent section.
Table 1 gives an indication of the enormous subsequent impact of von Laue’s
contribution by listing the Nobel Laureates who were recognised for their contributions to the development of this important structural technique. In the early days, the
winners were physicists who contributed to our understanding of the basic diffraction phenomenon. Specifically, the contributions of Arthur Compton and Louis de
Broglie resolved the wave/particle duality of small atomic particles which resulted
from the quantum mechanical description pioneered by Planck and Einstein and
demonstrated that such particles were capable of giving diffraction patterns through
their wave nature. Their insight was verified by Davisson and Thomson’s demonstration of diffraction patterns obtained when an electron beam was passed through a
crystal of nickel. Peter Debye defined the importance of thermal vibrations of atoms
in crystals, and he showed that microcrystalline samples also produced diffraction
patterns and thereby established X-ray powder diffraction, which proved to be so
important in metallurgy, materials science and solid-state chemistry. Although
Bragg’s initial contributions were made studying crystalline samples, he encouraged
his students to adopt a broader appreciation that the technique may be applied to
6
D. M. P. Mingos
regular disposition on the photographic plate were seen as conclusive evidence
that atoms are arranged regularly in a space-lattice configuration in crystals and
suggested the possibility of atomic resolution. As Alfred Tutton, the English crystallographer, overstated in November 1912, “the space-lattice structure of crystals
. . . is now rendered visible to our eyes” [21]. Within a year of the discovery of X-ray
diffraction, William Lawrence Bragg had reinterpreted the phenomenon responsible
for the diffraction pattern and determined the first unit cell dimensions of simple
salts, and within 2 years he and his father (William Henry Bragg) had reported the
first crystal structure determinations [19, 20, 23, 24]. The discoveries of von Laue
and Bragg gave birth to two new sciences, X-ray crystallography and X-ray spectroscopy, and two Nobel Prizes: Max von Laue “for his discovery of the diffraction
of X-rays by crystals” in 1914 and to the Braggs “for their services in the analysis of
crystal structure by X-ray Crystallography in 1915 (see Table 1).
Von Laue’s experiment had confirmed unambiguously the wave nature of X-rays
and suggested that the wavelength was sufficiently short that it gave rise to a
diffraction pattern from the target crystal. However, he did not completely or
succinctly articulate the physics which was responsible for the phenomenon. He
argued that the internal order of atoms within the crystal, which had been hinted at
for several centuries, results in a three-dimensional diffraction grating with spacings
much smaller than that commonly associated with visible light and their exposure to
X-rays resulted in the observed diffraction pattern. Specifically, the lack of knowledge concerning the nature of the lattice and the wavelength(s) of the X-rays limited
his contribution. Nonetheless, this seed of an idea rapidly grew and blossomed, and
it was able to draw on the circumstantial evidence which had been obtained
previously from optical crystallography which had been developed initially to
study mineralogical samples but was also used to study inorganic crystals made by
chemists in the nineteenth century. This cross fertilisation is discussed in more detail
in the subsequent section.
Table 1 gives an indication of the enormous subsequent impact of von Laue’s
contribution by listing the Nobel Laureates who were recognised for their contributions to the development of this important structural technique. In the early days, the
winners were physicists who contributed to our understanding of the basic diffraction phenomenon. Specifically, the contributions of Arthur Compton and Louis de
Broglie resolved the wave/particle duality of small atomic particles which resulted
from the quantum mechanical description pioneered by Planck and Einstein and
demonstrated that such particles were capable of giving diffraction patterns through
their wave nature. Their insight was verified by Davisson and Thomson’s demonstration of diffraction patterns obtained when an electron beam was passed through a
crystal of nickel. Peter Debye defined the importance of thermal vibrations of atoms
in crystals, and he showed that microcrystalline samples also produced diffraction
patterns and thereby established X-ray powder diffraction, which proved to be so
important in metallurgy, materials science and solid-state chemistry. Although
Bragg’s initial contributions were made studying crystalline samples, he encouraged
his students to adopt a broader appreciation that the technique may be applied to
6
D. M. P. Mingos