In part A, it is known that the carbon is vaporized to a mixture of molecular species such as $C_1$, $C_2$, $C_3$, and etc., and the larger polyatomic species become increasingly important effect on their thermodynamic properties at the higher temperature and pressure. Though little is presently known about the vapor species above $C_5$, in some estimate it is usually known that $C_3$ species are dominant at a relative condition. To make up for the lack in experimental data for liquid carbon, the thermodynamic properties of liquid carbon are calculated over a wide range of temperature from the triple point to critical point, by using the significant liquid structures model which has been successfully applied to many liquids.
In part B, normal modes of solids HF, HCl, and polyethylene having the exciting spectrometric phenomena have been evaluated by taking the lowest temperature phase of these species in the solid. The solids HF and HCl have the same space group as $C_{2v}$, and polyethylene has a space group with $D_{2h}$.
The normal modes were obtained by the valence force field with modified force constants and a quantitative description of the normal mode is adjusted by the potential energy distribution (PED). From the PED, the most fittable force constants are also obtained.
We have intended to calculate the normal modes by using the smallest size of the model and the simple computational process. To remove the edge effects being occurred in constructing the single cluster model, different from the boundary condition being generally used up to now, the idea of pseudolattic method being successfully applied to M.O. calculations of solid was extended to normal mode analysis in order to give the same environment for all molecules in a chosen cluster.
By using the above valence force field and boundary condition, we obtain the assigned frequencies and compare those results with the results obtained by others.
In part C, normal modes of crystalline orthorhombic sulfur belonging to the space group $D_{2h}$-Fddd, have been evaluated by taking the lowest temperature phase in solid. Normal modes are obtained by the valence force field with modified force constants and a quantitative description of the mode is adjusted by the potential energy distribution.
Since the full crystal system of orthorhombic sulfur is so large, we intended to calculate the normal modes simply by constructing the imaginary box made by the infinite mass boundary. And the Raman experiment is done by using the more powerful Ar-Kr laser with lowering the temperature to $\sim10^\circ{K}$.
A. 액체탄소는 평형 상태에서 Vacancy와 Chained molecule이 공존하므로 이 Chained molecule이 적은 분자로 쪼개지면서 gas-like molecule이 된다고 여겨진다. 또한 액체 탄소는 고온 고압 하에서 존재하므로 electronic term등이 주요한 significant structure 액체모델을 사용하여 액체 탄소의 여러가지 열역학적인 성질을 예견하였다.
B. 분광학적으로 재미있는 성질을 갖고 있는 서로 다른 물질을 택하여, 여기에 여러 종류의 boundary condition을 적용시킴으로써 얻어지는 정좌표를 서로 비교, 분석, 연구하여 우리가 제안한 Pseudolattice 방법이 정 좌표에서도 고체상태의 성질을 잘 설명해주고 있음을 입증하였다.