Band Calculations on Ferroelectric and Piezoelectric Solids
Final rept. 1 Jun 1977-1 Oct 1978
GEORGIA UNIV ATHENS DEPT OF PHYSICS AND ASTRONOMY
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The main objectives of the original proposal were to calculate spontaneous and other polarization properties of polar and piezoelectric crystals. The purpose of the work was to aid in selecting the best pyroelectric materials to be used in pyroelectric image tubes. The crystals for which the main work effort was directed were NaNO2, BN, LiNbO3 and KNbO3. Using charge densities obtained from band calculations with this program, the following piezoelectric coefficients d21, d22, and d23 for sodium nitrite have been calculated. This was accomplished by calculating the changes in the electric polarization of sodium nitride for three different strains. The plain-wave- Gaussian mixed basis method has been employed to calculate crystalline energy bands for cubic boron nitride zinc-blende structure. These calculations agree favorably with experiment. The spontaneous polarization of LiNbO3 has been calculated and the value differs by 20 percent from the experimental value. Because Lithium Niobate contains so many electrons in a unit cell we were not able to do a thorough calculation on LiNbO3 as was done on NaNO2.
- Electricity and Magnetism