最终作业

采用阶段能测试和k点测试脚本,分别绘制SiC原胞结构的总能随截断能变化曲线和SiC原胞结构的总能随k点的变化曲线,即收敛性测试

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    Phonon spectra of diamond

    1. Structural optimization (primitive cell of diamond)

    Please prepare the following files except the POTCAR (using vpot.py)

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    差分电荷和Bader电荷分布

    差分电荷分析(H2O分子为例)

    即成键后的电荷密度与对应的成键前的原子电荷密度之差。通过差分电荷密度的计算和分析,可以清楚地得到在成键和成键电子耦合过程中的电荷移动以及成键极化方向等性质。

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    过渡态理论以及Ammonia flipping计算实例

    • 当体系处于反应物或者产物的时候,整个体系为平衡态
    • 从反应物到产物的过程中至少有一个能量最高点,该点能量与反应物的差值即为反应所需要跨越的势垒,其活化能
    • 反应路径至少一条

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    晶体结构力学性能相关计算(VASP)

    晶体结构优化

    参考之前金刚石结构的优化过程,获得准确的金刚石晶格参数

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    金刚石(100)表面电子结构计算

    关于半导体表面重构的原理可以参考这一篇文献,讲的非常详细和基础。

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    建模

    建立合理的物理模型是理论计算的基础工作,建立的理论模型要尽可能与实验测试或制备结果相一致。
    科学高效的利用晶体结构数据库

    获得晶体结构数据:

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      Calculate the band structure and density of states of diamond with the VASP code

      *Note: This tutorial is for beginners only.

      In the previous chapter, we have completed the structure optimization of diamond and obtained the optimized diamond crystal structure using the PBE functional. In this section, we will complete the calculation of diamond band and electron state density.

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      Some useful scripts

      Cutoff energy test

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      #!/bin/sh
      #=====================================================
      # - FileName: Energy test of diamond
      # - Created: Dong Fan
      # - Email: fandong[at]outlook.com
      # - Copyright: Dong Fan
      #=====================================================

      cat>KPOINTS<<!
      K-Mesh
      0
      Monkhorst-Pack
      8 8 8
      0.0 0.0 0.0
      !
      ###ENCUT test
      for i in `seq -w 400 20 800`
      do
      cat > INCAR << !
      System = test_energy
      PREC = A
      ISTART = 0
      ICHARG =2
      ENCUT = $i
      EDIFF = 1e-5
      EDIFFG = -0.01
      IBRION = 2
      NSW=500
      ISIF = 2
      ISMEAR = 0;SIGMA = 0.05
      LCHARG = F
      LWAVE = F
      NPAR = 4
      !

      echo "ENCUT= $i eV"

      yhrun -N 1 -n 24 -p work vasp_std > vasp.log 2>&1

      E=`grep "TOTEN" OUTCAR | tail -1 | awk '{printf "%12.6f\n",$5}'`
      echo $i $E >> tet_ENCUT.dat
      done

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      INCAR parameter of VASP

      1. The bold part is the common control parameters.
      2. The annotations are all from the official manual of VASP.

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