建模过程:进入MS-Build-Crystals-选择点群-输入晶格参数-输入原子位置(这里是一个Mn原子位置,两个O原子位置)
问题:
(1)相临O原子之间的间隔非常小(~0.5 Angstrom),这样的晶体结构是"好"的晶体吗?
(2)这样的模型可以作为输入结构来计算吗?
根据后面所附的ICSD建的模型如下:

ICSD数据如下:
*data for ICSD #78331
CopyRight ?2005 by Fachinformationszentrum Karlsruhe, and the U.S. Secretary of
Commerce on behalf of the United States. All rights reserved.
Coll Code 78331
Rec Date 1996/04/22
Mod Date 1999/01/19
Chem Name Manganese Oxide - Gamma
Structured Mn O2
Sum Mn1 O2
ANX AX2
Min Name Ramsdellite
D(calc) 4.88
Title A powder neutron diffraction study of lambda and gamma manganese
dioxide and of Li Mn2 O4
Author(s) Fong, C.;Kennedy, B.J.;Elcombe, M.M.
Reference Zeitschrift fuer Kristallographie (149,1979-)
(1994), 209, 941-945
Unit Cell 9.3229(11) 4.4533(7) 2.8482(3) 90. 90. 90.
Vol 118.25
Z 4
Space Group P n a m
SG PNAM
SG Number 62
Cryst Sys orthorhombic
Laue Class mmm
Pearson oP12
Wyckoff c3
R Value .0427
Symmetry 1 x+.5, -y+.5, z
2 x, y, -z+.5
3 -x+.5, y+.5, z+.5
4 -x, -y, -z
5 -x+.5, y+.5, -z
6 -x, -y, z+.5
7 x+.5, -y+.5, -z+.5
8 x, y, z
Red Cell P 2.848 4.453 9.322 90 89.999 89.999 118.251
Trans Red 0.000 0.000 -1.000 / 0.000 1.000 0.000 / 1.000 0.000 0.000
Comments PDF 44-142. R(Bragg)=0.0134
Compound with mineral name: Ramsdellite
Neutron diffraction (powder)
The structure has been assigned a PDF number: 44-142.
Rietveld profile refinement applied
Calculated density unusual but tolerable.
Atom # OX SITE x y z SOF H ITF(U)
Mn 1 +4 4 c 0.1203(15) 0.0130(33) 0.25 1. 0 0
O 1 -2 4 c 0.0356(15) 0.2311(15) 0.75 1. 0 0.025(3)
O 2 -2 4 c 0.2842(12) 0.2934(20) 0.25 1. 0 0
Lbl Type U11 U22 U33 U12 U13 U23
Mn1 Mn4+ 0.020(4) 0.029(5) 0.017(3) 0.013(4) 0 0
O2 O2- 0.006(3) 0.050(5) 0.008(3) -.027(3) 0 0
*end for ICSD #78331
[ Last edited by cenwanglai on 2010-6-3 at 22:49 ] |