目前我們研究群光學的模擬計算都只是呈現出材料的整體線性的光學性質,並不會深入探討材料中各能帶其各別的貢獻,但經過對程式的修改,我們可以很容易的對光譜做能帶解析的動作。另外一般認為有機晶體的倍頻性可直接由分子的第一階超極化率,配合該分子在晶體中的排列方向來疊加構成,但利用第一原理計算來探討 MMONS 分子晶體化對於超極化率的影響時,我們可以看出分子晶體的倍頻係數並不是單純單分子倍頻係數的向量總合,並對其發生的機制做詳細的探討。最後藉由推導三階電極化率的公式我們希望了解與建立公式跟計算模擬程式間的對應,以便於未來對三階電極化率計算方法的發展。 The optical calculation within our research group nowadays just presents the optical properties of the entire material, it can not tell the individual contribution from each energy bands; but by modifying the calculating program, we can easily perform the band-resolved optical spectra. It is often believed that the second order susceptibility of a molecular crystal can be directly expressed in terms of the hyperpolarisibility of it constituent molecules, by using first principle calculation to study the effect of molecular crystallization, we will see that this is not always true; and discussing the results. Finally, through the derivation of third order susceptibility, we hope to understand and establish the correspondence of formulation and program code; this will be useful for the future research and code development in our research group.