ケイ酸塩溶融体/ガラスのMD計算について− 無機物の分子シミュレーション−

Abstract

無機化合物のMD計算を念頭において，高分子様の構造を持つ無機凝集体について構造などの概要を示し，古典分子動力学法による2元系ケイ酸塩溶融体/ガラスの計算における構造緩和の問題を述べる．また無機凝集体のMD計算の困難さ，意義，および必要性について述べる．

Translated Abstract

Structural features of inorganic polymer, oxoate compounds like silicate, are described. Then molecular dynamics simulations of sodium silicate melt / glasses were carried out using an empirical inter atomic potential model. The behavior of the energy and structural relaxation were investigated. The Q-species (the most important characters describing structure of silicate) change during an (NPT)-MD, show no obvious systematic change even in the clear energy relaxation. The difficulty of discussing the relation between energy-structure relaxation was shown. The necessity of computational methods of inorganic solids are discussed.

Figures

Figure 1.

 Enthalpy (●) and density (◆) as function of temperature of the N18000 system of Na2O·2SiO2 melt/glass. The arrow indicate the direction of relaxation with time in (NPT)-MD calculations.

Figure 2.

 Results of (NPT)-MD calculations at 1273. 15 K and 0.1 MPa of N5400 system. Enthalpy and density are plotted in upper graph, and Q-species and O^2- ratio (×) are plotted in lower graph.

Figure 3.

 Results of (NPT)-MD calculations at 1273.15 K and 0.1 MPa of N9000 system. Enthalpy and density are plotted in upper graph, and Q-species and O^2- ratio (×) are plotted in lower graph.

Figure 4.

 Results of (NPT)-MD calculations at 1273.15 K and 0.1 MPa of N18000 system. Enthalpy and density are plotted in upper graph, and Q-species and O^2- ratio (×) are plotted in lower graph.

Figure 5.

 Results of (NPT)-MD calculations at 1273.15 K and 0.1 MPa of N36000 system. Enthalpy and density are plotted in upper graph, and Q-species and O^2- ratio (×) are plotted in lower graph.

Figure 6.

 Q_n distribution of Na₂O·2SiO₂ melt/glass as a function against temperature. MD calculated molar fractions of Q_n species of the N18000 system are displayed.

Tables

Table 1. The number of atoms and cell edge length of each system

		Basic cell
System	No. atoms	Edge length/Å(1273.15 K)
N5400	5400	43.13
N9000	9000	51.19
N18000	18000	64.48
N36000	36000	81.43

Table 2. Ratio of Q species in the N18000 system.

T/K	Q0	Q1	Q2	Q3	Q4
1773.15	0.24	3.93	21.52	44.40	29.90
1673.15	0.38	4.16	21.03	43.73	30.69
1573.15	0.24	3.56	20.96	45.96	29.28
1473.15	0.33	3.25	21.88	43.88	30.66
1373.15	0.17	3.89	20.19	45.92	29.83
1273.15	0.16	3.81	20.14	45.79	30.09
1173.15	0.16	3.27	20.60	46.00	29.98
1073.15	0.19	3.45	20.08	45.67	30.62

References

• [1]S． Shimokawa，， H． Maekawa． E． Yamada，Y． Nakamura， and T． Yokokawa， Chem． Lett．， 617 (1990/4)
• [2]   T． Maehara， J. Non-Cryst. Solids， 351， 3685 (2005)． doi:10.1016/j.jnoncrysol.2005.10.003
• [3]K． Kawamura， MXDORTO， Japan Chemistry Program Exchange， #029 (1996)