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辉石四面体中有两种键。一种为桥键(以下简写为br),将四面体连接到键内;另一种为非桥键(以下简写为nbr)。各四面体皆有两个桥式键和两个非桥式键。NaM～(3+)Si_2O_6辉石中四面体内Si-O平均距离取决于M～(3+)离子的大小。设M～(3+)离子的大小影响桥键Si-O(br)距离和非桥键Si-O(nbr)距离,则其差值d_(br-Δ)和d_(nbr-Δ)与M～(3+)离子大小无关。式中,△为NaM～(3+)Si_2O_6辉石与NaAlSi_2O_6辉石中四面体Si-O平均距离((?):Prewitt和Burnham,1966)间的差值,d_(br-Δ)为Si-O(br)距离的平均值与△之间的差值。 Si-O距离依赖于非四面体阳离子的电负性、电子结构及其大小,这一点Ohashi(1981)已对NaM～(3+)Si_2O_6辉石作了检测。在Sc-V-Al序列中,d_(br-Δ)随着M～(3+)离子的电负性的增强而减小,而d_(nbr-Δ)则随着电负性的增强而增大。在该序列中,八面体位置被在t_2g态中有一个以上的空3d轨道的M～(3+)离子占据。在Cr-In-Fe序列中,Si-O(nbr)距离的平均值随电负性的增强而增大,而差值d_(br-Δ)随电负性的增强而减小。在该序列中,八面体位置被在t-2g态中不含空3d轨道的M～(3+)离子占据。本次研究的目的就是弄清NaTiSi_2O_6辉石是否具有以上相关关系。
There are two types of pyroxene tetrahedra. One is a bridge (abbreviated as br), which connects the tetrahedron to the key, and the other is a non-bridge bond (abbreviated as nbr). Each tetrahedron has two bridge keys and two non-bridge keys. The average distance of Si-O in tetrahedra in NaM ~ (3 +) Si_2O_6 pyroxenes depends on the size of M ~ (3+) ions. Assuming that the size of M ~ (3+) ions affects the distance of bridge Si-O (br) and the distance of non-bridge Si-O (nbr), the difference d_ (br-Δ) and d_ (nbr-Δ) M ~ (3+) ion size has nothing to do. In the formula, Δ is the difference between the average distance of Si-O tetrahedrons in NaM 3+ Si 2 O 6 pyroxenes and NaAlSi 2 O 6 pyroxenes ((?): Prewitt and Burnham, 1966), and d br br -O (br) The difference between the average of the distance and Δ. The Si-O distance depends on the electronegativity, electronic structure and size of the non-tetrahedral cation, as Ohashi (1981) has tested NaM 3+ Si 2 O 6 pyroxene. In the Sc-V-Al sequence, d_ (br-Δ) decreases with increasing electronegativity of M_ (3+) ions and d_ (nbr-Δ) decreases with increasing electronegativity Increase. In this sequence, octahedral positions are occupied by M ~ (3+) ions that have more than one empty 3d orbitals in the t_2g state. In the Cr-In-Fe sequence, the average Si-O (nbr) distance increases with increasing electronegativity and the difference d_ (br-Δ) decreases with increasing electronegativity. In this sequence, octahedral sites are occupied by M ~ (3+) ions that do not have an empty 3d orbit in the t-2g state. The purpose of this study is to find out whether NaTiSi_2O_6 pyroxene has the above correlation.