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A crystal or crystalline solid is a solid material whose constituents, such as atoms, molecules or ions, are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.
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- How does it happen that once a crystal is started, it permits only a particular kind of atom to join on? It happens because the whole system is working toward the lowest possible energy. A growing crystal will accept a new atom if it is going to make the energy as low as possible. But how does it know that a silicon—or an oxygen—atom at some particular spot is going to result in the lowest possible energy? It does it by trial and error. In the liquid, all of the atoms are in perpetual motion. Each atom bounces against its neighbors about 1013 times every second. If it hits against the right spot of growing crystal, it has a somewhat smaller chance of jumping off again if the energy is low. By continually testing over periods of millions of years at a rate of 1013 tests per second, the atoms gradually build up at the places where they find their lowest energy. Eventually they grow into big crystals.
- Richard Feynman: (1964). 30–3. The growth of crystals in Chapter 30. The Internal Geometry of Crystals, Vol. II, The Feynman Lectures in Physics
- You would, at first sight, think that a low-energy electron would have great difficulty passing through a solid crystal. The atoms are packed together with their centers only a few angstroms apart, and the effective diameter of the atom for electron scattering is roughly an angstrom or so. That is, the atoms are large, relative to their spacing, so that you would expect the mean free path between collisions to be of the order of a few angstroms—which is practically nothing. You would expect the electron to bump into one atom or another almost immediately. Nevertheless, it is a ubiquitous phenomenon of nature that if the lattice is perfect, the electrons are able to travel through the crystal smoothly and easily—almost as if they were in a vacuum. This strange fact is what lets metals conduct electricity so easily; it has also permitted the development of many practical devices. It is, for instance, what makes it possible for a transistor to imitate the radio tube. In a radio tube electrons move freely through a vacuum, while in the transistor they move freely through a crystal lattice.
- Richard Feynman: (1965). 13–1. States for an electron in a one-dimensional lattice in Chapter 13. Propagation in a Crystal Lattice, The Feynman Lectures on Physics, Volume III, Quantum Mechanics
- Maybe tomorrow when He looks down
Every green field and every town
All of his children, every nation
There'll be peace and good, brotherhood…
Crystal blue persuasion.
- I feel like a white granular mass of amorphous crystals—my formula appears to be isomeric with Spasmotoxin. My aurochloride precipitates into beautiful prismatic needles. My Platinochloride develops octohedron crystals,—with fine blue florescence. My physiological action is not indifferent. One millionth of a grain injected under the skin of a frog produced instantaneous death accompanied by an orange blossom odor.
- Lafcadio Hearn, in a letter to George M. Gould (1889), in The Life and Letters of Lafcadio Hearn Volume I (1906), by Elizabeth Bisland, p. 462
- A crystal is like a class of children arranged for drill, but standing at ease, so that while the class as a whole has regularity both in time and space, each individual child is a little fidgety!
- Dame Kathleen Lonsdale, in Crystals and X-Rays (1948), Chapter I
- I shall never forget the sight. The vessel of crystallization was three quarters full of slightly muddy water—that is, dilute water-glass—and from the sandy bottom there strove upwards a grotesque little landscape of variously colored growths: a confused vegetation of blue, green, and brown shoots which reminded one of algae, mushrooms, attached polyps, also moss, then mussels, fruit pods, little trees or twigs from trees, here, and there of limbs. It was the most remarkable sight I ever saw, and remarkable not so much for its profoundly melancholy nature. For when Father Leverk ¨uhn asked us what we thought of it and we timidly answered him that they might be plants: “No,” he replied, “they are not, they only act that way. But do not think the less of them. Precisely because they do, because they try as hard as they can, they are worthy of all respect.”
- Thomas Mann, in Doktor Faustus (1947), Chapter III
- Tyndall declared that he saw in Matter the promise and potency of all forms of life, and with his Irish graphic lucidity made a picture of a world of magnetic atoms, each atom with a positive and a negative pole, arranging itself by attraction and repulsion in orderly crystalline structure. Such a picture is dangerously fascinating to thinkers oppressed by the bloody disorders of the living world. Craving for purer subjects of thought, they find in the contemplation of crystals and magnets a happiness more dramatic and less childish than the happiness found by mathematicians in abstract numbers, because they see in the crystals beauty and movement without the corrupting appetites of fleshly vitality.
- George Bernard Shaw, in Back to Methuselah (1921), Preface, The Poetry and Purity of Materialism, p. lxii