The measurement of c o n d u c t i v i t y o f semiconductors w i t h methods r e q u i r i n g m e t a l l i c c o n t a c t s s u f f e r f r o m s e v e r a l troubJei because o f t h e p r o p e r t i e s of metal-semiconductor c o n t a c t s , inc l u d i n g imperfect c o n t a c t i n g , especiall'y a t l o w temperatures and w i t h h i g h l y i n s u l a t i n g material. W e t r i e d , t h e r e f o r e , t h e c a T a c i t i v e method of c o n d u c t i v i t y measurements (I), which does not need m e t a l l i c c o n t a c t s w i t h the semiconductor, f o r t h e magnetoresistance e f f e c t w i t h t h e hope t o circumvent such d i ff i c u l t i e s . The method proved indeed t o be l a r g e l y f r e e from severe d i s t u r b i n g i n f l u e n c e s .The c o n d u c t i v i t y and i t s change i n a magnetic f i e l d i s determined from t h e frequency dependence of t h e loss angle of a condenser t h a t c o n t a i n s the semiconducting medium (1 mm t h i c k n e s s ) between two i n s u l a t i n g mylar s h e e t s (10 p t o t a l t h i c k n e s s ) . The m a x i m a l magnetic f i e l d was 19.2 kG. The f r equency ranged f r o m 60 H e t o 20 MHz. The measurements could be made f o r t h e t r a n s v e r s e and t h e l o n g i t u d i n a l e f f e c t s (and f o r o r i e n t a t i o n s i n between) at temperatures between 60 and 295 OK. The c r y s t a l s were c i r c u l a r d i s k s of 1 mm t h i c k n e s s and 8 mm diameter; t h e i r s u r f a c e w a s perpendicular t o t h e [ I l l ] d i r e c t i o n .The r e s u l t s of the measurements w i t h Ge (n-type, donor c o n c e n t r a t i o n about 1 .5x101 ~m -~) agreed w e l l w i t h previous r e s u l t s f r o m current-voltage c h a r a c t e r i s t i c s methods ( 2 ) f o r t h e so-called "physical e f f e c t " (change o f m o b i l i t i e s i n t h e magnetic f i e l d ) i n s p i t e o f a geometry of t h e sample that would provoke a llgeometrical e f f e c t " (3). W e shall d i s c u s s t h i s circumstance i n a more d e t a i l e d r e p o r t t o be published l a t e r .Measurements w i t h G a A s (p-type at room temperature, Pe-5 physica
Medium sized basis sets of Gaussian Lobe functions for use in SCF-MO calculations are presented. With these, computations are performed on the hydrides of the atoms Li -F. Partly, mixed bases are applied in which the one-electron integrals are calculated with respect to a more extensive basis than the two-electron integrals. The energy shifts caused by shortening of the bases are separated into several components which are discussed in detail. Some conditions are given for that cases in which mixed basis calculations yield better results for energy and virial coefficient than uniform ones. These conditions are fulfilled by the function sets proposed.
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