Effect of particle size and shape on the free electron linear and nonlinear polarizabilities

摘要

A three-dimensional free electron model has been worked out to calculate the linear, alpha, and third-order, gamma, polarizabilities of nanosystems. The effect of shape has been investigated by comparing the response of a cubic box to that of plates and strips having the same volume and electron population. Reducing the box side 2L(z) along the z-axis induces a decrease in alpha(zz) and gamma(zzzz) and a corresponding increase in alpha(xx) (or alpha(yy)) and gamma(xxxx) (or gamma(yyyy)). The sign of alpha(xx) and a(zz) remain positive whereas those of gamma(xxxx) and gamma(zzzz) change from negative to positive. A similar behaviour appears when decreasing two box sides 2L(z) and 2L(y) but keeping constant volume and electron population. The results for the two limit cases, L-z --> 0 (thin plate) and L-z, L-y --> 0 (thin strip), have also been compared to those previously obtained by using two-and one-dimensional formulations, respectively. [References: 13]