SU1718070A1 - Method of determining crystallographic coordinates of crystalline body surface - Google Patents

Abstract

The invention relates to the physical science of materials and can be used to study the morphology of crystalline bodies. The purpose of the invention is to increase the efficiency of morphological research by obtaining more complete information. The essence of the method is that the uncut sample — after being monitored by a photogoniometric method — is placed, without changing the spatial position relative to the installation elements of the device, into an X-ray camera. After X-ray diffraction, the recorded diffraction pattern is compared to the light beam map obtained on the photogoniometer. After finding the correspondence between each light spot obtained from the faces, cleavage, and the crystallographic axes found by X-ray diffraction, accurate information is obtained about the crystallography of the faces of the strands, 4 or more. With y

Description

The invention relates to physical materials science and can be used to study the morphology of crystalline bodies. .

A known method for determining crystalline bodies consists in strengthening a crystal holder with a crystalline body on a movable support of a double-circle reflective goniometer, turning on a light beam, adjusting and centering the crystalline body, and systematically rotating it around vertical t; horizontal axes with visual determination in the optical tube of reflected rays from the face surfaces of the crystalline body and taking readings from the vertical and horizontal limbas, which give the spherical coordinates of the face surfaces on which their crystallographic coordinates are determined.

The closest in technical essence to the present invention is a method of photo goniometric determination of crystallographic coordinates of the face surfaces of crystalline bodies, including placing the crystalline body at the focus of a parabolic mirror in the required orientation, exposing it to the light flux and fixing the rays reflected from its faces on the photosensitive film, whose location is determined by the crystallographic coordinates of the face surfaces.

GAD

The disadvantage of this method is the impossibility of determining the crystallographic coordinates of the surfaces of any unlimited crystalline bodies due to the impossibility of visually determining their axes of symmetry for the necessary orientation of the crystalline bodies relative to the light beam. If it is impossible to show on the photosensitive film the direction of the axes of the coordinate frame of the crystal body, the determination of the coordinates of the surfaces is not possible.

The purpose of the invention is to increase the efficiency of morphological research by obtaining more complete information and expanding the field of application of the method by making it possible to determine the crystallographic coordinates of the face surfaces of any uncut crystal bodies (grains).

The goal is achieved by the fact that in the method of determining crystallographic coordinates of the surfaces of crystalline bodies, including placing the crystalline body at the focus of a parabolic mirror, exposing it to light and fixing the rays reflected from its face surfaces on the photosensitive film, after fixing the reflected rays on the photosensitive film to the crystalline body do not change its spatial orientation, direct a polychromatic beam of x-rays, record the laue The diffraction pattern on the film, uniquely oriented relative to the photosensitive film, establishes the position of the crystallographic axes of the studied crystal body in the coordinate system associated with the photosensitive film, and finds the spatial position of the normals to the face surfaces of the spot on the photosensitive film and the position of the crystallographic axes .

Figure 1 shows schematically the device of a photogonometer with a parabolic mirror; FIG. 2 shows a device for X-ray imaging of a fixedly reinforced crystalline body; FIG. on fig.Z - graphical determination of the coordinates X and Y of the trace of the light beam on the gnomonic projection of the surfaces of the crystalline body; Fig. 4 shows the distribution of X-rays during the X-ray survey. The Photogoniometer (Fig. 1) consists of a fixed source of light 1. A mirror 2 (parabolic) with a hole in the center for the passage of light rays is located in front of it. On the output side of the mirror, a tandem 3 is installed, which presumes a rectangular plate of organic glass with a hole on the axis of the mirror. A light-sensitive film is placed in the gap between the edge of the mirror with the plate. The crystal holder 4 consists of a cylindrical rod, having the ability to move along the axis of the device and rotate. At the front end of the crystal holder, a magnetic crystal carrier 5 is installed, which is a magnetic cylindrical plate with a plasticine cone fixed on it, to which crystal 6 is attached. (The arrow shows the direction of the primary and reflected light rays). A laser or a collimator can be used as a light source 1.

An X-ray imaging device (universal camera KRON-2, standard camera KROS) consists of an x-ray tube 7 (figure 2). In front of her on a stand 9,

5 perpendicular to the axis of the tube, the cassette 8 with the central hole for the passage of the x-ray beam, in which the x-ray film is inserted, is strengthened. Metal is installed on the same stand.

0 a cus plate 10 with a magnetic crystal carrier 5 located on the device axis and a crystal 6 fixed on it. The distance from the cassette to the crystal is .35 mm (the arrow shows the direction of

5 X-rays);

The essence of the proposed method is as follows.

The crystalline body 6 is reinforced with the help of clay at the end of a magnetic

0 of the crystal carrier 5, which is transferred to the end of the crystal holder 4. A photosensitive film is inserted into the cassette 3. With the help of the crystal holder, the crystal body is introduced into the focus of the mirror 2, including the source 1. The light exposes the photograph. On the crystal bearer note the vertical direction. Then the crystalline carrier with a crystalline body, without changing its spatial orientation,

0 is mounted on a metal plate 10 and placed in an x-ray chamber. An X-ray film is inserted in cassette 8. The inclusion of x-ray tube 7 for some time produced exposure

5 x-ray film.

When a crystalline body (polyhedron) is illuminated with a parallel beam of light rays from differently oriented sections of its surface, the reflection of primary rays is observed, the angle p of incidence

rays equal to the angle of reflection. When these rays are secondary reflected from a parabolic mirror, they fall on the photosensitive film. The position of the ray traces on the film plane is determined using the modified polar parabola equation.

 + ecos2p

where P is the parameter of the parabola;

e-eccentricity.

The coordinates of the traces of the rays on the film are determined by the formula

y l-sln2jO x l-cos2p (2)

, P vsln2p

y-lWcosTp

(3)

Equation (3) corresponds to the analytical expression of the gnomonic projection of the surfaces of the crystalline body. The parabolic sign P and measuring p in the picture y are used to determine p (Fig. 3). However, since the orientation of the axes of the coordinate frame of the crystal body relative to the primary beam is unknown, the calculated angle p is not true. To obtain a true grist, it is necessary to determine the spatial orientation of the crystalline body. For this, without changing its spatial orientation, the crystalline body together with the crystalline bone is transferred into the x-ray chamber and fixed on a special stand. Include x-ray beam, shoot a lauegram. The fall of a crystal body, an x-ray beam with a wavelength A, is reflected from one of the crystal planes bJ only at an angle a that will satisfy the Wolfe – gBregg equation,

The rays reflected from these planes are fixed on the X-ray film, and the angle a of incidence (or reflection) can be determined from the relation

1920

where I is the spot distance to the center of the radiograph,

D is the distance from the crystal body to the x-ray film (Fig. 4).

The location of the X-ray traces on the X-ray film depends on the degree to which the corresponding planes are oriented relative to the primary beam.

The orientation of the crystalline body is determined from the resulting lauegram. For this, the angles characterizing the positions of the reflecting planes on the stereographic projection are determined by formula (1). With their help, a stereographic projection of the crystalline body is constructed in the orientation studied. By measuring the angles between the planes on the obtained stereographic projection and comparing 5 of them with the most characteristic angles between the faces of the ideal crystal of this crystalline body, the characteristic angles, planes and axes of the coordinate frame are determined. lattices, assign them the corresponding indices and calculate their angular coordinates p (l (p.

Knowing the direction of the axis of the coordinate frame of the crystal body determines the true values of the angles of the brush or graphically, comparing the tomonomic projection of the crystalline substance obtained on the photosensitive film with the gnomonic projection of the ideal crystal of the same substance in the studied

0, or mathematically, calculating the angles obtained on the photosensitive film in the new coordinate system, taking the axis of the coordinate frame of the highest order in ocbZ.

5 The advantage of the proposed method is that it provides the ability to determine the crystallographic coordinates of the surfaces of any uncut crystalline bodies.

0 In a laboratory setup that implements the proposed method, a paragonic photogonometer and a URS-50 X-ray unit were used. A helium laser forming a parabolic mirror — 5 cm, diameter —15 cm was used as the light source in the photogoniometer5. When taking photographs using a photogoniometer, an FT-41 photographic film was used, the senses.

0 0.75 units

As laboratory tests have shown, the time required for the morphological study of a batch of raw materials of precious and semi-precious stones out of 100 pieces. (of which 30%

5 crystals) is equal to the time of visual mi: a non-ralogical description (partly using a photogoniometer), one with the sun. a batch of raw materials (100 pcs.) prepared for processing operations. In the case of visual

0 of the mineralogical description, only about 30% of the raw materials enter processing, and 70% are rejected. Thus, the application of the proposed method provides a high utilization rate of the primary raw material in preparing it for processing.

Claims (1)

The formula was invented and the Method of determining the crystallographic coordinates of the surfaces of crystalline bodies, which consists in placing the crystalline body at the focus of a parabolic mirror, directs a light beam at it and fixes it on the photosensitive film of the spot from the rays reflected from the cutting planes, characterized in that in order to increase the efficiency of morphological research by obtaining more complete information, the crystal body, without changing its spatial position, is directed polychromatic beam rzntgeno) L I / .L. . / 0 For example, a Laue diffraction pattern is recorded on a film that is uniquely oriented relative to the photosensitive film, the position of the crystallographic axes of the studied crystal body in the coordinate system associated with the photosensitive film is found, and the spatial position of the normals of the facet is determined on the position of the spot on the photosensitive film and the position of the Kristaploffmeer axes. fV n 0W.7 Phi gz Fi.g ig.ch