ATOMIC CHARGE SUPERPOSITION CALCULATIONS OF STM IMAGES OF 2D-ORDERED AMINO ACID ADSORBATES(Ⅱ)

In the preceding paper, we have successfully used the atomic charge superposition (ACS) method to calculate STM images of 2D-ordered structures of glycine molecules adsorbed on graphite (HOPG). In this work we focus on alanine/HOPG system. Firstly, we make a thorough searching for all of the possible 2D-ordered aggregation structures that can form linear chains or 2D nets of hydrogen bonds between the molecules and simultaneously satisfy the Van der Waal's radii of the condtituent atoms, just like in the case of 3D crystal of the molecules. Secondly, in order to interpret the experimental images, we use the ACS method to calculate STM images of the possible structures. It turns out that many of the experimental images can be interpreted satisfactorily with their calculated counterparts. This result further exhibits the great potential of using STM to study organic and biological molecules.     

双酚-S环氧树脂与琥珀酸酐固化反应动力学

用差示扫描量热法（ＤＳＣ）研究了双酚－Ｓ环氧树脂（ＢＰＳＥＲ）与琥珀酸酐固化反应的历程。实验结果表明,固化反应主要分两个阶段,前期由化学动力学控制,服从自催化机理。实验数据利用Ｋａｍａｌ方程处理得到两个速率常数ｋ、、ｋ２及两个反应级数ｍ、ｎ、ｋ１、ｋ２的值随反应温度的升高呈增大的趋势,总反应级数ｍ＋ｎ在２～２．５之间,当转化率达到４０％左右后,由于交联程度增加,分子量迅速增长,分子间扩散较慢,进入     

ATOMIC CHARGE SUPERPOSITION CALCULATIONS OF STM IMAGES OF 2D-ORDERED AMINO ACID ADSORBATES(Ⅰ)

In a previous STM investigation by Yang and co-workers a variety of 2D ordered atomic-scale features of glycine molecules adsorbed on graphite were observed and several models have been proposed to interpret these features. In the present work, atomic charge superposition(ACS) calculations of STM images of their models were carried out. The calculated images match the experimental ones fairly well, indicating the general validity of the ACS method to the glycine/graphite system and the correctness of their interpretations. The reason of the validity, the origin of the atomic resolution, and the proper tip-sample distance are also discussed.     

ATOMIC CHARGE SUPERPOSITION CALCULATIONS OF STM IMAGES OF 2D-ORDERED AMINO ACID ADSORBATES(Ⅰ)

In a previous STM investigation by Yang and co-workers a variety of 2D ordered atomic-scale features of glycine molecules adsorbed on graphite were observed and several models have been proposed to interpret these features. In the present work, atomic charge superposition(ACS) calculations of STM images of their models were carried out. The calculated images match the experimental ones fairly well, indicating the general validity of the ACS method to the glycine/graphite system and the correctness of their interpretations. The reason of the validity, the origin of the atomic resolution, and the proper tip-sample distance are also discussed.