Liao Ebin,

The reference can be found in "Semiconductor Sensors" edited by S. M.
Sze, Chapter 4, pp160-166 (1994).

The coefficients in the <111> silicon surface are as follows, the
numbers in parenthesis are coefficient index. And pi(L), and pi(T) are
longitudinal and transverse coefficients respectively.

pi(L)=1/3(pi(11)+2pi(12)+2pi(44))
pi(T)=1/3(pi(11)+2pi(12)-pi(44))

Also refer to the general calculation of the coefficients in any
direction given in the text.

Sunil
UFL