| | 1 | Author
| Gerhard Raabe | Requires cookie* | | | Title
| The Use of Quantum Chemical Semiempirical Methods to Calculate the Lattice Energies of Organic Molecular Crystals. Part I: The Three Polymorphs of Glycine  | | | | Abstract
| A method to calculate the lattice energies of organic molecular crystals is described. It is based on the semiempirical quantum chemical MINDO/3 approximation but might also be used within the framework of any other quantum chemical method. The lattice energy is approximated by the sum of dispersion-, induction-, exchange repulsion-, and electrostatic energy. Different, however, from other schemes employed in this field, like for example the atom-atom-potential method, the variables in the expression for the lattice energy have not been fitted to reproduce experimental values and, therefore, the single contributions retain their original physical meaning. Moreover, the method offers the advantage that it may be directly applied to all compounds that can be treated within the framework of the underlying quantum chemical method. Thus, time consuming readjustment of the entire parameter set upon extension of the group of target molecules by another class of compounds becomes obsolete. As an example, the lattice energies of the three polymorphs of glycine are calculated. | | | |
Reference
| Z. Naturforsch. 55a, 609—615 (2000); received March 11 2000 | | | |
Published
| 2000 | | | |
Keywords
| Lattice Energy, Glycine, Semiempirical Methods | | | |
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| default:Reihe_A/55/ZNA-2000-55a-0609.pdf | | | | Identifier
| ZNA-2000-55a-0609 | | | | Volume
| 55 | |
| 2 | Author
| Berthold Brazel, Rudolf Hoppe | Requires cookie* | | | Title
| Über Oxoplumbate(rV) Die Kristallstruktur von TT-Li2Pb03 [1] On Oxoplumbates(IV) The Crystal Structure of LT-Li2Pb03 [1] | | | | Abstract
| For the first time single crystals of LT-Li2Pb03 have been prepared by decomposition of K2Li6[Pb20s] [incompletely closed Ag cylinders, sealed in Supremax-glass ampoule, vacuum, 690°C, 100 d]. The structure determination [533Io(hkl); four-circle-diffractometer PW1100, co -scan, Mo -Ka, R = 4,86%, Rw = 4,93% confirms space group C2/c with a = 544.52(7), 6 = 926.12(7), c = 547,56(8) pm, ß = 111.216(13)°, Z = 4, drö = 6.94 g-cm" 3 , dpyk = 6.89 g • cm -3 . The NaCl-type structure variant is characterized by alternating layers of Li(2)+ and Li(l)+/Pb 4+ ~ cations. All atoms have octahedral coordination. The Madelung Part of Lattice Energy, MAPLE, Effective Coordination Numbers, ECoN, these via Mean Fictive Ionic Radii, MEFIR, are calculated. | | | |
Reference
| Z. Naturforsch. 37b, 1369—1374 (1982); eingegangen am 23. Juni 1982 | | | |
Published
| 1982 | | | |
Keywords
| Lithiumoxoplumbate(IV), Single Crystal Preparation, Structure, Lattice Energy | | | |
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| default:Reihe_B/37/ZNB-1982-37b-1369.pdf | | | | Identifier
| ZNB-1982-37b-1369 | | | | Volume
| 37 | |
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