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donggaomin金蟲 (正式寫手)
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[求助]
請(qǐng)問(wèn)VASP5.2中如何設(shè)置INCAR才可以計(jì)算(gamma點(diǎn)的)phonon frequency?
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請(qǐng)問(wèn)VASP5.2中如何設(shè)置INCAR才可以計(jì)算(gamma點(diǎn)的)phonon frequency? 說(shuō)明書上只說(shuō)了設(shè)置IBRION = 6 另外,怎么查看結(jié)果?論壇里提到是動(dòng)力學(xué)矩陣的對(duì)角化,不是很明白。我知道動(dòng)力學(xué)矩陣對(duì)角化后是頻率的平方。 謝謝! VASP5.2中是不是可以計(jì)算phonon frequency? |
聲子譜 |

金蟲 (正式寫手)
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補(bǔ)充:這是在VASP論壇中找到的: you can calculate the gamma-point phonons with vasp.4.6, using a frozen phonon approach please use IBRION=5 in that case, and set POTIM = 0.015 (as the harmonic limit is assumed) in case you do not need all modes, please use the Selective dymanics key in POSCAR and just allow the vibrations you are intrested in (by setting F/T ) in order to save CPU time. it is not possible to continue a broken phonon job (keeping the info) it has to be restarted from the beginning. relativistic effects can be simulated by using spin-orbit splitting (please have a look at the LSORBIT tag, and the additional parameters you have to set. 這是第二個(gè) To do \Gamma point phonon calculate Firstly, fully relax your structure and save WAVECAR Secondly, you can start a phonon calculation by set INCAR as PREC= Accurate ADDGRID = .TRUE. ENCUT= 500.00 eV ISTART=1 ICHARG=0 IBRION= 6 NFREE=4 POTIM=0.015 !displacement of atoms in Ang. IALGO= 48 LREAL=Auto !needed for good convergence NSIM = 4 LCHARG = .False. LPLANE=.TRUE. ~ 現(xiàn)在的問(wèn)題是:是不是第二個(gè)的方式好點(diǎn)?如何查看結(jié)果? |

金蟲 (正式寫手)

金蟲 (正式寫手)
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下面是設(shè)置了IBRION = 6時(shí)的動(dòng)力學(xué)矩陣本征值,按我的理解是本征值就是頻率的平方,但... 請(qǐng)問(wèn)怎么看下面的結(jié)果呢? Eigenvectors and eigenvalues of the dynamical matrix ---------------------------------------------------- 1 f = 15.937321 THz 100.137142 2PiTHz 531.611795 cm-1 65.911486 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.000519 -0.000028 0.081397 1.609613 0.929267 2.583248 -0.000519 -0.000028 -0.081397 -0.000113 1.858561 1.976701 0.001581 0.000057 -0.702404 1.609613 0.929267 4.559948 0.001581 0.000057 0.702404 2 f = 13.134427 THz 82.526040 2PiTHz 438.117317 cm-1 54.319644 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.092238 -0.254007 0.000249 1.609613 0.929267 2.583248 0.092238 0.254007 0.000249 -0.000113 1.858561 1.976701 -0.222415 -0.614413 -0.000695 1.609613 0.929267 4.559948 0.222415 0.614413 -0.000695 3 f = 13.116478 THz 82.413261 2PiTHz 437.518595 cm-1 54.245412 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.254559 -0.092022 0.000439 1.609613 0.929267 2.583248 -0.254559 0.092022 0.000439 -0.000113 1.858561 1.976701 0.614185 -0.222503 -0.000963 1.609613 0.929267 4.559948 -0.614185 0.222503 -0.000963 4 f = 12.231166 THz 76.850683 2PiTHz 407.987772 cm-1 50.584055 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.128882 -0.287868 -0.000033 1.609613 0.929267 2.583248 -0.128882 -0.287868 0.000033 -0.000113 1.858561 1.976701 0.258437 0.577694 0.000731 1.609613 0.929267 4.559948 0.258437 0.577694 -0.000731 5 f = 12.215895 THz 76.754733 2PiTHz 407.478389 cm-1 50.520900 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.288034 0.128850 -0.000113 1.609613 0.929267 2.583248 -0.288034 0.128850 0.000113 -0.000113 1.858561 1.976701 0.577610 -0.258454 0.001474 1.609613 0.929267 4.559948 0.577610 -0.258454 -0.001474 6 f = 10.927284 THz 68.658148 2PiTHz 364.494939 cm-1 45.191629 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.000189 0.000636 0.313532 1.609613 0.929267 2.583248 0.000189 -0.000636 0.313532 -0.000113 1.858561 1.976701 -0.000728 0.000873 -0.633795 1.609613 0.929267 4.559948 0.000728 -0.000873 -0.633795 7 f = 7.595291 THz 47.722620 2PiTHz 253.351625 cm-1 31.411609 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.000310 0.000022 0.702406 1.609613 0.929267 2.583248 0.000310 0.000022 -0.702406 -0.000113 1.858561 1.976701 0.000072 -0.000016 0.081397 1.609613 0.929267 4.559948 0.000072 -0.000016 -0.081397 8 f = 2.947281 THz 18.518311 2PiTHz 98.310698 cm-1 12.188977 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.129670 0.640455 -0.000783 1.609613 0.929267 2.583248 -0.129670 -0.640455 -0.000783 -0.000113 1.858561 1.976701 -0.053713 -0.264796 -0.000086 1.609613 0.929267 4.559948 0.053713 0.264796 -0.000086 9 f = 2.934466 THz 18.437793 2PiTHz 97.883244 cm-1 12.135980 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.640217 -0.129724 0.000119 1.609613 0.929267 2.583248 -0.640217 0.129724 0.000119 -0.000113 1.858561 1.976701 -0.265373 0.053582 0.000117 1.609613 0.929267 4.559948 0.265373 -0.053582 0.000117 10 f/i= 0.003591 THz 0.022565 2PiTHz 0.119792 cm-1 0.014852 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.000007 -0.000665 -0.633795 1.609613 0.929267 2.583248 -0.000007 0.000665 -0.633795 -0.000113 1.858561 1.976701 -0.000005 0.000373 -0.313533 1.609613 0.929267 4.559948 0.000005 -0.000373 -0.313533 11 f/i= 0.036145 THz 0.227107 2PiTHz 1.205674 cm-1 0.149485 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.063064 0.629725 -0.000046 1.609613 0.929267 2.583248 0.063064 0.629725 0.000046 -0.000113 1.858561 1.976701 0.031392 0.313821 0.000019 1.609613 0.929267 4.559948 0.031392 0.313821 -0.000019 12 f/i= 0.039877 THz 0.250556 2PiTHz 1.330159 cm-1 0.164919 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 0.629641 -0.063053 -0.000333 1.609613 0.929267 2.583248 0.629641 -0.063053 0.000333 -0.000113 1.858561 1.976701 0.313989 -0.031415 0.000203 1.609613 0.929267 4.559948 0.313989 -0.031415 -0.000203 |

金蟲 (著名寫手)
金蟲 (著名寫手)
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舉例 1 f = 15.937321 THz 100.137142 2PiTHz 531.611795 cm-1 65.911486 meV X Y Z dx dy dz -0.000113 1.858561 0.000000 -0.000519 -0.000028 0.081397 1.609613 0.929267 2.583248 -0.000519 -0.000028 -0.081397 -0.000113 1.858561 1.976701 0.001581 0.000057 -0.702404 1.609613 0.929267 4.559948 0.001581 0.000057 0.702404 第一行就是頻率,不同的單位給出。 后面X Y Z是原子坐標(biāo) 在后面的 dx dy dz是動(dòng)力學(xué)矩陣的本征矢量,判斷振動(dòng)類型的時(shí)候用到。 |
專家顧問(wèn) (職業(yè)作家)
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專家經(jīng)驗(yàn): +83 |
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說(shuō)的很好,補(bǔ)充幾點(diǎn): 5用的是差分,6用的是DFPT,感覺好像DFPT更靠譜一點(diǎn)。不過(guò)貌似VASP的計(jì)算結(jié)果沒有PWSCF的好,而且只能算gamma點(diǎn)的。 dx,dy,dz是本征矢,也是震動(dòng)方向,有時(shí)做一些強(qiáng)度或者是穩(wěn)定性計(jì)算的時(shí)候可能會(huì)用到。 |
專家顧問(wèn) (職業(yè)作家)
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專家經(jīng)驗(yàn): +83 |
金蟲 (著名寫手)
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是的,有限差分的可信度取決于原子的位移 因?yàn)橛邢薏罘钟?jì)算Hessen矩陣是 Hij=d2E/dxidxj=[E(ri0+dxi,rj0+dxj)+E(ri0-dxi,rj0-dxj)-2E(ri0,rj0)]/dxidxj 上面的d是微分,rjo就是j原子的平衡位置,E是能量。 上式反映出位移xi, xj不能太大。 太小的話位移后構(gòu)型的能量和沒位移的構(gòu)型的能量沒差別,也會(huì)導(dǎo)致誤差。 還有一個(gè)誤差,有些體系會(huì)遇到,就是VASP中計(jì)算頻率是簡(jiǎn)諧近似,忽略了能量對(duì)位移泰勒展開的高階項(xiàng)。 我測(cè)試過(guò)H2,CO分子,合理選擇位移的話,計(jì)算值和實(shí)驗(yàn)值差別在10cm-1以內(nèi)。 |
金蟲 (正式寫手)

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