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New crystal structure maps have been proposed on the basis of the DV-X α molecular orbital calculations of electronic structures. Two electronic parameters have been introduced and employed as new parameters for the classification of crystal structures. One is the bond order and the other is the d-orbital energy level of elements. Both of them change following the position of elements in the periodic table. With these parameters crystal structure maps have been constructed for aluminides, silicides, and some transition-metal-based compounds. There is a clear separation of the crystal structures on the maps. These maps are found to be applicable to the prediction of crystal structures not only for binary compounds but also for ternary compounds. The possibilities of structural modification of Nb 3 Al and Al 3 Ti by alloying are also discussed with the aid of these maps.

The influence of a number of alloying elements on the electronic structure of aluminium has been investigated by the DV-X, cluster method. The energy level structure was modified remarkably by alloying. For transition metals, for instance. this modification was mainly due to the appearance of the virtual bound state of d electrons near the Fermi energy level. Except for a few elements, the ionicities of alloying elements change monotonically following the electronegativity. The bond order between atoms largely depends on the alloying elements, while the activation energy for the 3d impurity diffusion in aluminium can be related to the calculated bond order. An increment of the residual resistivity, due to the 3d impurities doped into aluminium, also correlata well with the virtual bound stale densityat the Fermienergylevel. Inaddition, it isshown fromcalculations that Mn and Cr are probably the magnetic impurities in aluminium.

An noncontact ultrasonic motor, which is composed of two metal disks for a low-profile configuration and 30 mm in diameter, is proposed. To enhance rotation characteristics, the resonant mode of the air gap between the stator and rotor is chosen to coincide with the resonance of stator vibration both in frequency and mode shape. The motor rotated at 1,260 rpm with the (1,1) flexural vibration mode of the disk stator, driven at about 25 kHz.