臺灣博碩士論文加值系統

自旋極化的第一原理虛函數(pseudofuction)計算方法，及局部電子自旋密度近似法(local spin density approximation)被使用來計算，在壓力下反鐵磁與鐵磁狀態之砷化鎳(NiAs)結構的碲化錳(MnTe)塊材的總能量、電子結構與總能態密度(TDOS)和部分電子能態密度(PDOS)。在此研究中所考慮的壓力範圍內，在熱力學上反鐵磁狀態比鐵磁狀態更穩定，與實驗結果吻合。反鐵磁狀態的碲化錳的非直接能隙，會隨著壓力的增加而線性的減小，此現象和實驗結果一致。由計算的結果可發現價帶與傳導帶的寬度，隨壓力增加而變寬，此現象可歸因為因壓力影響碲化錳的鍵長使其變短，以致於銻和碲軌道的耦合增強所造成。

The spin polarized first principles pseudofunction (PSF) method with the local spin density approximation (LSDA) has been used to calculate total energies, electronic structures and total and partial densities of states for bulk MnTe in the NiAs structure for both anti-ferromagnetic and ferromagnetic states under the pressure. For the pressure range considered in this study, the anti-ferromagnetic state is thermodynamically more stable than the ferromagnetic state in agreement with experimental observation. For the anti-ferromagnetic state, MnTe has an indirect band gap, which decreases linearly with the increase of the pressure in agreement with experiment. The calculated valence band and conduction band are found to broaden with the increase of the pressure, which can be attributed to the pressure induced shortening of the Mn-Te bond length that enhances hybridization between Mn and Te orbitals.

I. Introduction 1
II. Theory
2-1 The density functional theory (DFT)
with the local-spin-density approximation(LSDA) 3
2-2 The pseudofunction (PSF) calculation method 8
III. Calculation details 14
IV. Results and Discussion 16
V. Summary 20
References 21
Table Caption 24
Figure Caption 25
Tables 27
Figures 29

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