科研神器 | 带你了解X射线衍射仪（XRD）

<section style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; color: rgba(0, 0, 0, 0.9); font-family: 'PingFang SC', system-ui, -apple-system, BlinkMacSystemFont, 'Helvetica Neue', 'Hiragino Sans GB', 'Microsoft YaHei UI', 'Microsoft YaHei', Arial, sans-serif; font-size: 17px; letter-spacing: 0.544px; text-align: justify; background-color: #ffffff; visibility: visible; box-sizing: border-box !important; overflow-wrap: break-word !important;"> <section style="margin: 10px 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; text-align: left; justify-content: flex-start; display: flex; flex-flow: row nowrap; visibility: visible;"> <section style="margin: 0px; padding: 0px; outline: 0px; max-width: 100%; box-sizing: border-box !important; overflow-wrap: break-word !important; display: inline-block; width: auto; vertical-align: top; min-width: 10%; flex: 0 0 auto; height: auto; overflow: hidden; align-self: flex-start; visibility: visible; border: 0px none #3e3e3e;"> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><a title="X射线衍射仪（XRD）" href="https://www.kexingtest.com/instrument/detail?id=226" target="_blank" rel="noopener"><span style="color: rgba(0, 0, 0, 0.901960784313726); font-family: Microsoft YaHei UI, sans-serif;"><span style="letter-spacing: 0.533333px;"><strong>X射线衍射仪</strong></span></span></a><strong style="color: rgba(0, 0, 0, 0.9); font-family: 'PingFang SC', system-ui, -apple-system, BlinkMacSystemFont, 'Helvetica Neue', 'Hiragino Sans GB', 'Microsoft YaHei UI', 'Microsoft YaHei', Arial, sans-serif; font-size: 12pt; letter-spacing: 0.544px;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">的工作原理</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">x</span><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">射线的波长和晶体内部原子面之间的间距相近，晶体可以作为<span lang="EN-US">X</span>射线的空间衍射光栅，即一束<span lang="EN-US">X</span>射线照射到物体上时，受到物体中原子的散射，每个原子都产生散射波，这些波互相干涉，结果就产生衍射。衍射波叠加的结果使射线的强度在某些方向上加强，在其他方向上减弱。分析衍射结果，便可获得晶体结构。</span></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">1. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">我想知道不同衍射角对应的晶面，怎么办？</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">如果你的图能够找到对应的粉末衍射数据卡，那么问题就简单了。多数的粉末衍射数据卡上面都给出了各衍射线的衍射指标，也就可以知道对应的晶面了。<span lang="EN-US"> </span></span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">如果是未知晶体结构的图，就需要求解各衍射线的衍射指标，这一步工作叫做“衍射图的指标化”。如自己解决需要具备基础的晶体学知识，然后学会一两个指标化的工具软件（如<span lang="EN-US"> treaor90</span>）进行尝试。</span></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">2. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">对于正交晶系的晶胞参数，其中<span lang="EN-US"> a</span>、<span lang="EN-US">b</span>、<span lang="EN-US">c </span>代表晶胞的三个棱的长度。但我不清楚如何定义<span lang="EN-US"> a</span>、<span lang="EN-US">b</span>、<span lang="EN-US">c </span>的方向，也就是说按照什么依据确定这三条棱的方向？是否有明确的规定还是可以任意自定义？</span></strong></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">一般来说可以用<span lang="EN-US"> a < b < c </span>的定向原则，其实，用什么方向都可以，它们可以通过矩阵来转换。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">晶胞中的<span lang="EN-US"> a</span>，<span lang="EN-US">b</span>，<span lang="EN-US">c</span>，分别是三个晶轴方向上的单位平移向量的长度，称为轴长，不是“三个棱”的长度。轴长符号也常用<span lang="EN-US"> a0</span>，<span lang="EN-US">b0</span>，<span lang="EN-US">c0 </span>表示。轴长单位常用<span lang="EN-US">Å</span>（埃，<span lang="EN-US">Angstrom</span>） 或纳米（<span lang="EN-US">nm</span>）。在晶体结构中没有“棱”这样一种说法，只有晶体坐标系，而这个坐标系是用<span lang="EN-US"> a</span>，<span lang="EN-US">b</span>，<span lang="EN-US">c</span>，α，β，γ 六个参数来表示的，α，β，γ 分别代表三个轴间的夹角。而”晶棱“是指晶体的外形的棱边。所以说”<span lang="EN-US">a</span>、<span lang="EN-US">b</span>、<span lang="EN-US">c </span>代表晶胞的三个棱的长度“是错误的。</span></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">3. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">如何计算晶胞体积？比如说我想计算二氧化锆四方晶相的晶胞体积，甚至是各个晶胞参数， 怎么用这个软件来具体处理一下呢？</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">首先，你要有相应的晶体学方面的知识。这些软件是为我们处理一些晶体学上的一些问题服务，所以，你不能抛开晶体学去使用软件。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">有了一些必要的晶体学知识之后，你再去学习 使用这些软件，这样你才能看懂<span lang="EN-US"> help </span>里的内容。对于你现在所讲的这个晶胞体积的问题， 实际上也就是晶胞参数精确测定的问题，因为晶胞参数精确测定了之后，晶胞体积自然就知道了。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">4. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">有什么软件能根据分数坐标画出晶体的空间结构？就是有八面体或者四面体的那种。</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">根据晶体的结构数据，用<span lang="EN-US"> diamond </span>或<span lang="EN-US"> atoms </span>等专业的晶体结构绘图软件便可画出晶体的空间结构。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">5. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">六角结构的晶体在生长时它的内在的优先生长方向是哪一个？</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">一般来说晶体沿短轴方向生长速度快<span lang="EN-US"> ,</span>垂直于长轴方向的晶面密度较大，从能量的角度说，当晶体生长时，这样的格位更稳定一些。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">6. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">如何知道晶体中原子坐标？</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">做单晶<span lang="EN-US"> X</span>－射线衍射才能得到原子的坐标。除了四圆外，<span lang="EN-US">CCD </span>也可进行单晶<span lang="EN-US"> X</span>－射线衍射。</span></span></p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><strong><span lang="EN-US" style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">7. </span></strong><strong><span style="font-family: 'Microsoft YaHei UI', sans-serif; color: #009688; letter-spacing: 0.4pt;">如何根据<span lang="EN-US"> X </span>射线衍射数据计算晶粒尺寸晶格常数和畸变，用什么理论和公式？</span></strong></span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"> </p> <p style="margin: 0cm; margin-bottom: .0001pt;"><span style="font-size: 12pt;"> </span></p> <p class="MsoNormal" style="mso-pagination: widow-orphan;"><span style="font-size: 12pt;"><span style="font-family: 'Microsoft YaHei UI', sans-serif; letter-spacing: 0.4pt;">根据衍射峰的峰形数据可以计算晶粒尺寸晶格常数和畸变。在衍射峰的宽化仅由于晶粒的细小产生的情况下，根据衍射峰的宽化量用<span lang="EN-US"> Scherrer </span>公式便可以估算晶粒在该衍射方向上的厚度。</span></span></p> </section> </section> </section>