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49003新蟲 (初入文壇)
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[求助]
hse雜化泛函計(jì)算能帶,導(dǎo)帶和價(jià)帶整體上移0.4eV是什么原因 已有1人參與
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我應(yīng)用的是標(biāo)準(zhǔn)化晶胞結(jié)構(gòu),a = b = 20.3Å,操作步驟為: 1.結(jié)構(gòu)優(yōu)化,INCAR文件如下: #### initial I/O #### ISTART = 1 ICHARG = 1 LWAVE = .FALSE. LCHARG = .TRUE. LVTOT = .FALSE. LVHAR = .FALSE. LELF = .FALSE. # LORBIT = 11 # NEDOS = 2000 #### Ele Relax #### ENCUT = 500 # 截?cái)嗄,越高表示精度越高,默認(rèn)400eV ISMEAR = 0 # 和SIFGMA一起決定在做布里淵區(qū)積分時(shí),如何計(jì)算分布函數(shù)。絕緣體0-0.05,金屬1/2-0.2,態(tài)密度-5,SIGMA不設(shè)置 SIGMA = 0.05 EDIFF = 1E-5 # 控制自洽優(yōu)化收斂的能量標(biāo)準(zhǔn),即前后兩次能量差小于這個(gè)值則收斂完成。默認(rèn)1E-4 NELMIN = 5 #電子自洽的最小步數(shù),默認(rèn)為2 NELM = 300 #電子自洽的最大步數(shù),默認(rèn)60 GGA = PE #交換關(guān)聯(lián)勢(shì)的類型,VASP會(huì)根據(jù)POTCAR自動(dòng)確定(我們用的贗勢(shì)庫(kù)所對(duì)應(yīng)的為PE),也可不用設(shè)置 LREAL = .FALSE.# 表面計(jì)算用Auto。決定投影算符在實(shí)空間還是倒空間計(jì)算,高精度計(jì)算用FALSE,在超過(guò)20個(gè)原子的系統(tǒng)中可以設(shè)置成Auto。 ISYM = 0 # 確定是否打開對(duì)稱性,1、2、3為打開對(duì)稱性,-1、0關(guān)閉對(duì)稱性。 PREC = Normal # 控制計(jì)算精度的參數(shù),會(huì)影響多個(gè)參數(shù)比如ENCUT。一般默認(rèn)為Normal,高精度的計(jì)算比如聲子計(jì)算時(shí)需要設(shè)置成Accurate。 IVDW = 10 # DFT-D2矯正范德華力。11為D3矯正。 # LDIPOL = .TRUE.# 兩個(gè)控制表面偶極校正,對(duì)于上下表面不對(duì)稱,會(huì)引入偶極,但是SCF收斂變慢 # IDIPOL = 3 #### Geo opt #### EDIFFG = -0.001 # 設(shè)定結(jié)構(gòu)優(yōu)化的精度,正值表示能量,負(fù)值表示力,建議設(shè)置為負(fù)值(特別是聲子計(jì)算時(shí)需要設(shè)置更小的值) IBRION = 2 # 決定粒子如何運(yùn)動(dòng)。-1表示離子不動(dòng);0表示第一性原理分子動(dòng)力學(xué)模擬;1表示準(zhǔn)牛頓法進(jìn)行結(jié)構(gòu)優(yōu)化;2表示共軛梯度法進(jìn)行結(jié)構(gòu)優(yōu)化 POTIM = 0.2 # IBRION=0時(shí),為時(shí)間步長(zhǎng),單位為fs;在結(jié)構(gòu)優(yōu)化計(jì)算時(shí)(1\2\3),為力的縮放因子,默認(rèn)為0.5 NSW = 300 # 離子運(yùn)動(dòng)的最大步數(shù),在做結(jié)構(gòu)優(yōu)化和分子動(dòng)力學(xué)模擬中設(shè)置。默認(rèn)值為0,即離子不動(dòng)。 ISIF = 2 # 0-不計(jì)算應(yīng)力張量;1-結(jié)構(gòu)優(yōu)化時(shí)只計(jì)算總的應(yīng)力,只優(yōu)化離子位置。2~7計(jì)算應(yīng)力張量。2只讓離子位置做優(yōu)化,晶胞矢量不做優(yōu)化;3:同時(shí)優(yōu)化離子位置、原胞形狀和體積 ALGO=VeryFast #電子最優(yōu)化的算法。 #### Mag #### # ISPIN = 2 # 電子自旋極化的開關(guān)。默認(rèn)為1,非磁性計(jì)算,自旋非極化體系;2.自旋極化體系。簡(jiǎn)單磁性體系直接設(shè)置成2,magmom不必設(shè)置。 2.vaspkit302功能生成KPATH.in,這一步本來(lái)應(yīng)該生成PRIMCELL,但是我選了302功能之后沒(méi)有生成PRIMCELL文件,我就繼續(xù)用上一步結(jié)構(gòu)優(yōu)化生成的CONTCAR文件了。 3.vaspkit251,2,0.05,0.05功能生成KPOINTS文件。我的KPOINTS文件是: 0.050 1 1 1 1 0.050 15 3 5 5 5 # Parameters to Generate KPOINTS (Do NOT Edit This Line) 16 Reciprocal lattice 0.00000000000000 0.00000000000000 0.00000000000000 1 0.00000000000000 0.00000000000000 0.00000000000000 0 0.12500000000000 0.00000000000000 0.00000000000000 0 0.25000000000000 0.00000000000000 0.00000000000000 0 0.37500000000000 0.00000000000000 0.00000000000000 0 0.50000000000000 0.00000000000000 0.00000000000000 0 0.50000000000000 0.00000000000000 0.00000000000000 0 0.45833333332500 0.08333333332500 0.00000000000000 0 0.41666666665000 0.16666666665000 0.00000000000000 0 0.37499999997500 0.24999999997500 0.00000000000000 0 0.33333333330000 0.33333333330000 0.00000000000000 0 0.33333333330000 0.33333333330000 0.00000000000000 0 0.24999999997500 0.24999999997500 0.00000000000000 0 0.16666666665000 0.16666666665000 0.00000000000000 0 0.08333333332500 0.08333333332500 0.00000000000000 0 0.00000000000000 0.00000000000000 0.00000000000000 0 4.vaspkit生成HSE06自洽計(jì)算的INCAR: Global Parameters NCORE=4 ISTART = 1 (Read existing wavefunction, if there) ISPIN = 1 (Non-Spin polarised DFT) #ICHARG = 11 (Non-self-consistent: GGA/LDA band structures) LREAL = .FALSE. (Projection operators: automatic) ENCUT = 600 (Cut-off energy for plane wave basis set, in eV) # PREC = Accurate (Precision level: Normal or Accurate, set Accurate when perform structure lattice relaxation calculation) LWAVE = .TRUE. (Write WAVECAR or not) LCHARG = .TRUE. (Write CHGCAR or not) ADDGRID= .TRUE. (Increase grid, helps GGA convergence) # LVTOT = .TRUE. (Write total electrostatic potential into LOCPOT or not) # LVHAR = .TRUE. (Write ionic + Hartree electrostatic potential into LOCPOT or not) # NELECT = (No. of electrons: charged cells, be careful) # LPLANE = .TRUE. (Real space distribution, supercells) # NWRITE = 2 (Medium-level output) # KPAR = 2 (Divides k-grid into separate groups) # NGXF = 300 (FFT grid mesh density for nice charge/potential plots) # NGYF = 300 (FFT grid mesh density for nice charge/potential plots) # NGZF = 300 (FFT grid mesh density for nice charge/potential plots) Static Calculation ISMEAR = 0 (gaussian smearing method) SIGMA = 0.05 (please check the width of the smearing) LORBIT = 11 (PAW radii for projected DOS) NEDOS = 2001 (DOSCAR points) NELM = 60 (Max electronic SCF steps) EDIFF = 1E-08 (SCF energy convergence, in eV) HSE06 Calculation LHFCALC= .TRUE. (Activate HF) AEXX = 0.25 (25% HF exact exchange, adjusted this value to reproduce experimental band gap) HFSCREEN= 0.2 (Switch to screened exchange, e.g. HSE06) ALGO = ALL (Electronic Minimisation Algorithm, ALGO=58) TIME = 0.4 (Timestep for IALGO5X) PRECFOCK= N (HF FFT grid) # NKRED = 2 (Reduce k-grid-even only, see also NKREDX, NKREDY and NKREDZ) # HFLMAX = 4 (HF cut-off: 4d, 6f) # LDIAG = .TRUE. (Diagnolise Eigenvalues) 5.vaspkit252功能生成band能帶圖,這是我的生成結(jié)果: +-------------------------- Summary ----------------------------+ Band Character: Direct Band Gap (eV): 2.5392 Eigenvalue of VBM (eV): -5.4925 Eigenvalue of CBM (eV): -2.9533 HOMO & LUMO Bands: 99 100 Location of VBM: 0.000000 0.000000 0.000000 Location of CBM: 0.000000 0.000000 0.000000 官方的生成結(jié)果是: Band Gap: 2.5381 eV (HSE06) HOMO: -5.8981 eV (Ured = 1.88 V ) LUMO: -3.36 eV (Uox := 0.66 V) 我的結(jié)果和他的結(jié)果導(dǎo)帶和價(jià)帶的位置整體上移了0.4eV,求教這是什么原因? |
木蟲 (正式寫手)
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差約 0.4 eV 的整體向上移動(dòng)通常 不是 帶結(jié)構(gòu)計(jì)算里的“帶形狀”問(wèn)題(那會(huì)改變帶的相對(duì)位置/帶隙),更像是能量零點(diǎn)(reference)/電位對(duì)齊 或 計(jì)算細(xì)節(jié)不一致 導(dǎo)致的整體偏移。優(yōu)先檢查清單(我推薦的順序) 核對(duì) POTCAR(最易出錯(cuò)且常被忽略)。 確認(rèn)官方結(jié)果的能量零點(diǎn)(是相對(duì)真空還是相對(duì)平均電勢(shì)/費(fèi)米)。如果官方用了真空,按上面方法算真空電位并對(duì)齊。 做一次真正的 HSE 自洽 SCF(不要直接依賴 PBE CHGCAR),保存 CHGCAR,再用 ICHARG=11 做 band 采樣;比較結(jié)果。 輸出 LOCPOT,做平面平均找真空能級(jí),看你的 VBM/HOMO 相對(duì)真空是否與官方一致。 若仍不同,檢查 NELECT、是否帶電、偶極修正、KPOINTS。 |
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