第七章 晶体结构的点阵理论

第七章 晶体结构的点阵理论 组员：070601321 艳君 070601322 林露 070601323 洁洁 070601324 明颖 070601325林莹 070601326 俞鸿 070601347 潘渊 1.In the space lattice,it is sure to elect the prime unit(no matter what is the shape about parallel hexahedron)? Is it sure to elect the heart cubic lattice?how to elect it? Answer:yes, it was collected from four edges of the mid-point and connect and make up of a side. It is the heart of cubic lattice.

2. According to the proper division of dot-matrix units, the basic principles of the four categories of argument lattice plane lattice, only four types of rectangular units with a heart and without heart ，these two kinds of patterns, while others with no heart in the form.

Prove: Positive units, namely, high symmetry, with lattice fewer units.To meet the requirements of the flat shape of the proper lattice there are only four of five types, namely a square lattice, rectangular lattice, rectangular lattice with a heart, the six-party lattice and parallelogram lattice.As shown below：

Six lattice Square lattice Parallelogram lattice If the other forms of lattice structure containing snacks, then they will become free with a heart back to the form.

3.Use Two-dimensional graphics for example.Demonstration of non-collocated base stacking does not meet the requirements of translation.

Answer:For the two-dimensional structure.Cell should be designated a total of four cell,can we ensure that cell have the same fixed point on the

Rectangular lattice Rectangular lattice with a Heart environment. As shown in the figure,If each rectangle represents a structural motif, as point A and B point of the surrounding environment is different, (A point not connected to the top of the line, B-point bottom line is not connected) the figure of the rectangle is not a cell. Choose the composition of the red cell lines, and the formation of the formation of the structure of the unit cell and ordered home.

4. What is the relationship between the lattice structure and crystal? Space lattice and the lattice is done in response relationship or the same thing? Answer: These geometric point in space, arranged according to certain rules (cycle repeats) constitute a lattice. Different crystal, corresponding different lattice form.. But they have a common property. Connect any of the bright spots determined by the vector, line pan are able to recover. Lattice is a geometric forms reaction the crystal structure of a cyclical. Space lattice parallel to a defined division of hexahedral unit connection, obtain a set of straight-line grid, called space lattice or lattice.

5. Why heart cubic lattice type, but not four hearts lattice patterns? Answer：As shown, because the four aspects of mind can be replaced by four body-centered. No.5 6、Crystal plane diffraction indicators and targets and with links What's the difference? Answer：The diffraction of indicators that diffraction and reciprocal lattice points (h, k, l) the relationship between the symbols, denoted by hkl. Diffraction index and crystal plane index difference is: three integers h, k, l need not be coprimed. An integer index hkl diffraction determines the direction of the crystal diffraction discrete nature of each set of indicators provides a diffraction diffraction direction. With a group of crystal surface spacing d (hkl), parallel beam X-rays reach all parts of the crystal face family, the incident angle of θ. Crystal face resulting diffraction conditions for family: 2 d (hkl) sinθn = nλ

7.As shown in the figure,For the layer-shaped molecules form a two-dimensional graphite crystal, its structure motifs in addition to map outside the electoral law, but also with how to choose? Derived from a variety of election law in both the structure of the base element contains several C? Number of C --- C bond length? Answer: 2 C. 2 C --- C bond length 3C. 3 C --- C bond length

4/3C. 1C --- C bond length 10/3C. 5C --- C bond length 8. Write a diamond cubic lattice of carbon atoms in fractional coordinates, given the cell parameters a=356.7pm, Calculation the bond length of C-C. Answer: Known the atomic coordinates of C is （0，0，0）and（ 14 , 14 , 16 ）

R= （x2－x1）2+(y2－y1)2+(z2－z1)2a Into the relevant data

R= （14 －0）2+( 14 －0)2+( 16 －0)2 ×356.7pm =139.5pm

9. An AB-type crystals, A and B in the cell,their coordinate parameters are （000）and（12 ， 12 ， 12 ）. Specified the crystal lattice type and structure of space-based element. Answer: A set of radio scattered factor fa, B set of radio scattered factor fb