A method for preparing large size beta-type ammonium tetramolybdate monocrystal particle includes industrial ammonium molybdate, ammonia, de-ionized water are used to prepare ammonium molybdate solution with concentration of 0.2˜0.6 g/ml; pH is adjusted to 5˜7, temperature is adjusted to the first temperature of 70˜90° C. to obtain the first ammonium molybdate solution; beta-type ammonium tetramolybdate crystal seed is put into crystallization container, and the first ammonium molybdate solution is poured in the crystallization container, to form crystallization system; the crystallization system stands still at room temperature, naturally cooling, the beta-type ammonium tetramolybdate crystal seed grows into large size beta-type ammonium tetramolybdate monocrystal particle. A beta-type ammonium tetramolybdate crystal seed is obtained by constant-temperature crystallization at 70˜90° C. The obtained beta-type ammonium tetramolybdate crystal seed is put stewing in the first ammonium molybdate solution and is naturally cooling to produce large size beta-type ammonium tetramolybdate monocrystal particle forms.

A method for preparing large size beta-type ammonium tetramolybdate monocrystal particle includes industrial ammonium molybdate, ammonia, de-ionized water are used to prepare ammonium molybdate solution with concentration of 0.2˜0.6 g/ml; pH is adjusted to 5˜7, temperature is adjusted to the first temperature of 70˜90° C. to obtain the first ammonium molybdate solution; beta-type ammonium tetramolybdate crystal seed is put into crystallization container, and the first ammonium molybdate solution is poured in the crystallization container, to form crystallization system; the crystallization system stands still at room temperature, naturally cooling, the beta-type ammonium tetramolybdate crystal seed grows into large size beta-type ammonium tetramolybdate monocrystal particle. A beta-type ammonium tetramolybdate crystal seed is obtained by constant-temperature crystallization at 70˜90° C. The obtained beta-type ammonium tetramolybdate crystal seed is put stewing in the first ammonium molybdate solution and is naturally cooling to produce large size beta-type ammonium tetramolybdate monocrystal particle forms.

A pyramidal growth method for long-seed KDP-type crystal. In the growth method provided by the present invention, the lower end of the long-seed crystal is restricted by a lower tray, and the upper end is free to grow into a pyramidal. At the same time, the four prismatic faces at two directions of [100] and [010] can grow, avoiding growth stress problem during crystal growth, and all cut optical elements have high optical quality. Because the growth process is that four prismatic faces with highly similar growth environments grow at the same time and stirring is applied by blade-like stirring paddles during the crystal growth process, the cut optical elements have high optical uniformity.

A pyramidal growth method for long-seed KDP-type crystal. In the growth method provided by the present invention, the lower end of the long-seed crystal is restricted by a lower tray, and the upper end is free to grow into a pyramidal. At the same time, the four prismatic faces at two directions of [100] and [010] can grow, avoiding growth stress problem during crystal growth, and all cut optical elements have high optical quality. Because the growth process is that four prismatic faces with highly similar growth environments grow at the same time and stirring is applied by blade-like stirring paddles during the crystal growth process, the cut optical elements have high optical uniformity.

An organic thin film includes an organic solid crystal material and has mutually orthogonal refractive indices, n.sub.x, n.sub.y, and n.sub.z each having a value at 589 nm of between approximately 1.5 and approximately 2.6, where n.sub.x≠n.sub.y≠n.sub.z. The organic thin film may be birefringent, and may be configured as a single layer thin film, or plural organic thin films may be stacked to form a multilayer that may be incorporated into an optical element, such as a reflective polarizer.

An organic thin film includes an organic solid crystal material and has mutually orthogonal refractive indices, n.sub.x, n.sub.y, and n.sub.z each having a value at 589 nm of between approximately 1.5 and approximately 2.6, where n.sub.x≠n.sub.y≠n.sub.z. The organic thin film may be birefringent, and may be configured as a single layer thin film, or plural organic thin films may be stacked to form a multilayer that may be incorporated into an optical element, such as a reflective polarizer.

A method for screening a target compound for polymorphic forms is provided. The method comprises providing a library of mixed-crystal seeds, each mixed-crystal seed consisting essentially of the target compound and at least one structural analog that is structurally analogous to the target compound; and for each mixed-crystal seed: introducing the mixed-crystal seed into a crystallization medium comprising the target compound, under conditions suitable for crystallization of the target compound; monitoring the formation of crystals of the target compound; and when formed, characterizing the crystals of the target compound.

A method for screening a target compound for polymorphic forms is provided. The method comprises providing a library of mixed-crystal seeds, each mixed-crystal seed consisting essentially of the target compound and at least one structural analog that is structurally analogous to the target compound; and for each mixed-crystal seed: introducing the mixed-crystal seed into a crystallization medium comprising the target compound, under conditions suitable for crystallization of the target compound; monitoring the formation of crystals of the target compound; and when formed, characterizing the crystals of the target compound.

A post-synthetic method for stabilizing colloidal crystals programmed from nucleic acid is disclosed herein. In some embodiments, the method relies on Ag.sup.+ ions to stabilize the particle-connecting nucleic acid duplexes within the crystal lattice, essentially transforming them from loosely bound structures to ones with very strong interparticle links. In some embodiments, the nucleic acid is DNA. Such crystals do not dissociate as a function of temperature like normal DNA or DNA-interconnected colloidal crystals, and they can be moved from water to organic media or the solid state, and stay intact. The Ag.sup.+-stabilization of the nucleic acid (e.g., DNA) bonds is accompanied by a nondestructive contraction of the lattice, and both the stabilization and contraction are reversible with the chemical extraction of the Ag.sup.+ ions, e.g., by AgCl precipitation with NaCl.

A post-synthetic method for stabilizing colloidal crystals programmed from nucleic acid is disclosed herein. In some embodiments, the method relies on Ag.sup.+ ions to stabilize the particle-connecting nucleic acid duplexes within the crystal lattice, essentially transforming them from loosely bound structures to ones with very strong interparticle links. In some embodiments, the nucleic acid is DNA. Such crystals do not dissociate as a function of temperature like normal DNA or DNA-interconnected colloidal crystals, and they can be moved from water to organic media or the solid state, and stay intact. The Ag.sup.+-stabilization of the nucleic acid (e.g., DNA) bonds is accompanied by a nondestructive contraction of the lattice, and both the stabilization and contraction are reversible with the chemical extraction of the Ag.sup.+ ions, e.g., by AgCl precipitation with NaCl.