摘要:

A description is given of a fully automatic program, written in ALGOL 60, that finds the constants of the reciprocal lattice from powder data. The progress of the program is illustrated with the (nearly) complete computer output for one selected case. Planes through the origin of the reciprocal lattice (zones) are found first. After evaluating these, the program selects pairs of zones with a common row in order to find reciprocal lattices, which are then reduced in a simple way. Each solution is compared with the experimental data and a figure of merit is calculated. The program is most suited for compounds of orthorhombic or lower symmetry.

ISSN:1600-5767    

DOI:10.1107/S0021889869006649

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The α phase of the silver–magnesium alloy system containing 26.1 atomic per cent magnesium has been studied by X‐ray diffraction methods in the temperature range from 20 to 678°C. The tetragonal symmetry of the low‐temperature phase is confirmed. The temperature variation of the lattice parameters and the volume expansion coefficient have been determined. It seems likely that the order–disorder transformation is a first‐order rather than a second‐order t

ISSN:1600-5767    

DOI:10.1107/S0021889869006650

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The changes observed in the scattering pattern during the initial stages of ageing an Al–20 wt.% Ag alloy at 220°C are reported. Patterns containing both the halo (resulting from G.P. zones) and streaks (resulting from platelets of Ag2Al) have been recorded. An analysis of these streaks shows that the platelets are no more than 9 Å thick. This value is much smaller than that previously rep

ISSN:1600-5767    

DOI:10.1107/S0021889869006662

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The two principal components of the mean‐square atomic displacement resulting from thermal vibrations in holmium, 〈uz2〉 and 〈ux2〉, are determined from single‐crystal, X‐ray diffraction intensities, corrected for thermal diffuse scattering and for extinction effects. The room temperature values of 〈uz2〉 and 〈ux2〉 are found to be 0.01225 ± 0.00063 and 0.0122 ± 0.0021 Å2respectively. These two components of the average displacement combine to yield an X‐ray Debye temperat

ISSN:1600-5767    

DOI:10.1107/S0021889869006674

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A portable apparatus for cooling specimens used in X‐ray and neutron diffraction studies is described. Temperatures in the + 50 to −1 185 °C range can be automatically and continuously maintained within 1 ° of the desired temperature for several weeks. Cold gas is obtained from liquid nitrogen which is boiled off at a rate sufficient to maintain a constant pressure in the sealed Dewar. The temperature‐determining gas‐flow rate is controlled by a pneumatically operated cryogenic valve which responds to a thermocoup

ISSN:1600-5767    

DOI:10.1107/S0021889869006686

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A simple, inexpensive, and essentially foolproof apparatus is described for obtaining a constant temperature, constant flow of cold nitrogen gas for use in low‐temperature diffraction studie

ISSN:1600-5767    

DOI:10.1107/S0021889869006698

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The texture of commercially produced stabilized steel in the temper rolled condition has been represented by a three‐dimensional orientation distribution, defined by a set of coefficients of a series of generalized spherical harmonics. The coefficients have been used to calculate the elastic and plastic properties in the plane of the sheet and comparison is made between the predicted and experimental values. Errors in the experimental determination of pole figures have been analysed and estimate

ISSN:1600-5767    

DOI:10.1107/S0021889869006704

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

The method proposed in part I for the interpretation of small angle scattering data is applied to various concentrated systems. For a dilute system, small angle scattering provides the ϕ(l) distribution of chords directly in the scattering units. Two examples of dilute particle suspensions are studied: firstly rounded particles of polytetrafluoroethylene and secondly cubic microcrystals of MgO. Thus we have obtained the ϕ(l) distributions characteristic of particles with or without sharp edges. For concentrated systems, when the ϕ(l) distribution of particle chords is known, small angle scattering provides thef(m) distribution of interparticle spacings. The result, applied to a porous aggregate of the rounded particles, already studied in a dilute state, and to a concentrated suspension of the same particles, gives twof(m) distributions distinctly characteristic of each sta

ISSN:1600-5767    

DOI:10.1107/S0021889869006716

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

A 45° conical back reflexion camera has been found to be very suitable for single‐crystal orientation. A chart for the interpretation of the back reflexion films is describ

ISSN:1600-5767    

DOI:10.1107/S0021889869006728

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY

摘要:

It is shown experimentally that the flux at a point in a neutron beam from a collimator of a given angular divergence is very dependent on the length of the collimator. A simple geometrical theory fits the experimental results fairly well.

ISSN:1600-5767    

DOI:10.1107/S002188986900673X

出版商:International Union of Crystallography    

年代:1969

数据来源: WILEY