1、设有一维晶体的电子能带可写成(k)=dfrac ({h)^2}(m{a)^2}(dfrac (7)(8)-cos ka+dfrac (1)(8)cos 2ka), 其中(k)=dfrac ({h)^2}(m{a)^2}(dfrac (7)(8)-cos ka+dfrac (1)(8)cos 2ka)为晶格常数,(k)=dfrac ({h)^2}(m{a)^2}(dfrac (7)(8)-cos ka+dfrac (1)(8)cos 2ka)是电子的质量。试求(1)能带宽度;(2)电子在波矢k状态的速度; (3)带顶和带底的电子有效质量。

已知一维晶体的电子能带可写成:(k)=dfrac ({h)^2}(m{a)^2}(dfrac (7)(8)-cos ka+dfrac (1)(8)cos 2ka

cos dfrac (x)({2)^n})（提示：lim _(xarrow infty )(cos dfrac (x)(2)cos dfrac (x)(4)co

(sin x)=dfrac (1)({cos )^2x} in (0,dfrac (pi )(2)),则(sin x)=dfrac (1)({cos )^2x}

已知曲线积分(int )_(1)^1(1+dfrac ({cos )^2}({x)^2}cos dfrac (y)(x))dx+(sin dfrac (y)(x

计算(int )_(c)_(c)dfrac (cos z)((z-dfrac {1)(2))(z-1)}dz，其中(int )_(c)_(c)dfrac (co

(3) (int )_(0)^dfrac (pi {4)}dfrac (x)(1+cos 2x)dx= () .-|||-(A) dfrac (pi )(8)+

(int )_(-dfrac {pi )(2)}^dfrac (pi {2)}((cos )^2x+dfrac (xcos x)(1+{cos )^2x})dx

10.气相总阻力可表示为 dfrac (1)({K)_(6)}=dfrac (1)({K)_(6)}+dfrac (1)(H{K)_(1)}, 其中 dfrac

【题目】 (int )_(0)^dfrac (pi {2)}cos xdx= ()-|||-A、 dfrac (1)(2)-|||-B、1-|||-C、 -df

0 .dfrac (1)(2) .-|||--dfrac (1)(2) . .dfrac (1)(8) .dfrac (1)(6) .dfrac (1)(24)