1. Phonopy-Spectroscopy : It is a project to add the capability to simulate vibrational spectra to the Phonopy code. Features: Calculate infrared (IR) intensities from Phonopy or VASP calculations; Calculate Raman-activity tensors and scalar-averaged intensities within the far-from-resonance approximation; Prepare peak tables including assigning modes to irreducible representations (Phonopy interface); Output customisable simulated spectra with support for multiple unit systems and simulated instrumental broadening; Include first-principles mode linewidths from Phono3py calculations (Phonopy interface). https://github.com/JMSkelton/Phonopy-Spectroscopy When using this code, please cite the following article: Phy. Chem. Chem. Phy. 19, 12452 (2017). 2. IR : Python Package to Calculate IR Intensities from the Dipole Approximation with Phonopy and VASP. This python package can calculate infrared intensities based on the dipole approximation. To do so, you need VASP and Phonopy . https://github.com/JaGeo/IR When using this code, please cite the following article: J. Chem. Phys. , 1994 , 100 , 8537; J. Phys.:Condens. Matter. , 2010 , 22 , 265006. 3. INTENS : The BASH script for evaluation of IR intensities within DFPT by VASP. As of VASP 5.* version, the DFPT linear response calculations are available. Among others, the user can obtain the matrix of Born effective charges ( BEC ), which refers to change of atoms'polarizabilities at an external electric field. The BEC tensor is a key to calculate the vibrational intensities using the most modern method available , using the formula by Gianozzi Baroni. http://homepage.univie.ac.at/david.karhanek/downloads.html 4. raman-sc : Python program to evaluate off-resonance Raman activity using VASP code as the backend. In order to calculate off-resonance Raman activity of a mode, one needs to compute the derivative of the polarizability (or macroscopic dielectric tensor) with respect to that normal mode coordinate: dP/dQ (or de/dQ). Thus, two ingredients are required: Phonons at Γ-point; Macroscopic dielectric tensor. https://github.com/raman-sc/VASP 5. VASP2NMR : Convert VASP files to NMR spectra. https://github.com/smeerten/VASP2NMR 6. opticsVASP : Program to plot optical properties from VASP results Program to plotoptical properties from VASP results. compile the program with :$g++ -oopticsVASP opticsVASP.2.0.c. run the executable file on the folder where theVASP output files are located. https://github.com/gmsn-ita/opticsVASP
PHonon can be used whenever PWscf can be used, with the exceptions of DFT+U, nonlocal VdW and hybrid functionals. USPP and PAW are not implemented for higher-order response calculations. On Dec 7, 2009, at 24:01 , damien wrote: I wanted to know if, in a near future, it will be envisaged to have an implementation of Raman spectra with Ultra Soft or/and PAW pseudopotentials? You need to perform a 2nd-order response calculation to an electric field with USPP or PAW. It is not a trivial extension. P. --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 转自： http://www.democritos.it/pipermail/pw_forum/2009-December/015405.html
前几天使用pwscf计算金属的Raman光谱失败，所以就到Pw_forum上去寻找原因,似乎pwscf只能计算拥有带隙的系统的Raman光谱( they are well defined only for insulators ),它不能处理金属性体系的极化，或者说它处理极化的方法是针对半导体或绝缘体的，不适用于金属性体系。 On Jan 14, 2008, at 11:50 , Miriam Marques wrote: I am emailing a previous unanswered question. Is it possible to calculate Raman intensities for "metallic systems" such as hcp-metals: Zn, Fe, Zr, Mg, high pressure phases of oxygen or high pressure phases of alkali metals using the ESPRESSO code? it depends: what is the expression of Raman intensities in "metallic systems"? The usual definition of Raman intensities in the nonresonant limit via derivatives of the polarizabily (this is what is calculated in Q-E) does not apply to metals. P. --- Paolo Giannozzi, Dept of Physics, University of Udine via delle Scienze 208, 33100 Udine, Italy Phone +39-0432-558216, fax +39-0432-558222 from http://www.democritos.it/pipermail/pw_forum/2008-January/008152.html ============================================================= Dear Miriam: you and others will forgive my ignorance, but I would need some further explanations. According to the usual theory, they both should be zero:````````````````````` the second is given by Born effective charges (that are zero in metals), the former by the derivative of the inverse macroscopic electric constant (which is also zero). How can a metal be Raman or IR active? Thanks - SB On Dec 14, 2007, at 7:18 PM, Miriam Marques wrote: Dear ESPRESSO users, I would like to know if it is possible to compute Raman and Infrared intensities for a metallic system. Thank you very much in advance, Miriam. Dr. Miriam Marques Centre for Science at Extreme Conditions. The University of Edinburgh. e-mail: mmarques at staffmail.ed.ac.uk -- The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336. _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA DEMOCRITOS National Simulation Center - Trieste 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) from http://www.democritos.it/pipermail/pw_forum/2007-December/007975.html ==================================================================== 个人粗浅的以为：理论上来说，Raman的活性是polarization的改变，其实就是电子云形状的改变。在非晶体中，电子都被局限在晶格中，电子的运动都被局限于晶格之中，所谓的Raman活性检测到的其实是晶格的振动；而在金属晶体中，由于金属中的电子是自由运动的，可以说是一个大的电子气（不知道这种说法对不对），所以无法识别单个电子云形状的变化。不知道这样子理解对不对，请高手继续。 by pinguo from http://emuch.net/html/201001/1777354.html 金属没有拉曼光谱，拉曼测得是原子之间的键的振动，金属原子之间没有键，所以测不了 by nanbowan from http://bbs.instrument.com.cn/shtml/20110418/3255293/ 1. 拉曼光谱是分子光谱，而金属都是原子结构的，所以金属没有拉曼光谱。 2. 这个问题要看拉曼效应产生的原理了。金属中不存在分子的振动，当然就没有拉曼谱了. 3. 很多原子构成的物质都有拉曼信号，比如硅的520波数线.拉曼测的是振动能级，声子能量，反映晶格振动的量子化能量的大小.金属表面电子和原子实构成的等离子体对光有强烈的吸收(金属的高反射性能也与此有关)，使激光无法与内部原子作用，因此很难看到拉曼线.这是我根据自己已有知识的猜测，欢迎行内达人指正。 4. 也可以用光的波矢k为虚数来解释，当k为虚数时，光不能在此物质中传播。当然和光的频率w有关，用其它波长的光激发可以激发拉曼谱。 by haiying from http://bbs.antpedia.com/viewthread.php?tid=25951 拉曼效应起源于分子振动(和点阵振动)与转动，因此从拉曼光谱中可以得到分子振动能级(点阵振动能级)与转动能级结构的知识。楼主提出金属也有原子晶格的简谐振动，这个跟分子振动以及转动都不是一个概念，因为前者不涉及能级跃迁，而Raman谱反映能级信息的前提就是能级跃迁。Raman效应反映的不是分子简谐振动能级的信息，楼主可以仔细看看网页 http://baike.baidu.com/view/146359.htm ，我就不赘述了。 当然，楼主提出的其他3点都可以作为金属没有Raman特征峰的原因，归纳起来也就是一点：金属是具有电子自由气的原子晶体结构。 至于非晶为何没有Raman特征峰，我想原因可能是Raman特征峰是一个积分效果，需要晶体的周期性重复才能出来，对于非晶，某一位置的确发生拉曼散射，但是仪器是无法达到只有这一个或几个分子能级信息的精度，因此无法产生特征峰！ 一家之言，望讨论！ by from leongoall from http://emuch.net/html/201201/4010887.html
from http://www.st-andrews.ac.uk/seeinglife/science/research/Raman/Raman.html Raman spectroscopy Raman spectroscopy relies on the scattering of light. In the same way that particles can be scattered through collisions with other particles, light can also be deflected when it interacts with matter. Upon interaction with matter, there can be four different types of energy exchange . Why is the sky blue? The sky looks blue because the tiny particles of dust and water in the air scatter the light from the sun. Blue light has a shorter wavelength and is scattered more than red light so the sky appears blue. As the light from the sun travels through more atmosphere more of the colours of light are scattered and the sun appears red. Raman Scattering Only 1 in every 30 million photons are inelastically, scattered and the photon transfers some of its energy to the molecule Rayleigh (ordinary) scattering is when the photon is absorbed to a higher virtual level and is instantly scattered (emitted) elastically back to the initial level. The photons emitted by Stokes-Raman scattering usually have a lower energy and frequency than that of the photons absorbed and these photons are inelastically scattered, transferring some of their energy to the molecule. The reverse is also possible; the photons emitted have a higher energy and frequency than the photons absorbed. This is called Anti-Stokes-Raman, but it is not likely at room temperature as electrons prefer to be in the ground state. Raman Spectroscopy Raman Spectroscopy is a vibrational spectroscopy technique used to collect a unique chemical fingerprint of molecules. Each molecule has a different set of vibrational energy levels, and the photons emitted have unique wavelength shifts. Vibrational spectroscopy involves collecting and examining these wavelength shifts and using them to identify what is in a sample. Different peaks in the spectrum correspond to different Raman excitations. Uses Raman Spectroscopy produces information about a cell. It tells you about the state of the cell, and possibly whether or not it is virally infected and whether or not it is cancerous, precancerous, or not cancerous. It can be used to study HIV and malaria. A laser is shone at the cell and the information needed is extracted from the spectra obtained. Enhancements Unfortunately Raman scattering is a rare event, roughly 1 in every 30 million photons is Raman scattered. This means that it takes a long time to get a signal, which can also be highly masked by fluorescence or other interference. An improved signal to noise ratio is required to reduce acquisition time. A laser is normally used as a light source to increase the photon density. The photons from the laser, with frequency in the visible range, provide monochromatic excitation. Another way to enhance Raman spectroscopy is to make the virtual level in the Jablonski diagram above a real level. Normally no energy level actually exists at this energy value. This process is called resonance Raman scattering . It chooses an incident wavelength at which the molecular unit absorbs and selectively excites the vibrations of this unit. Surface enhanced Raman spectroscopy (SERS), is another technique used to improve Raman based on metallic surfaces that has proved to be very successful, and by combining Raman spectroscopy with optical trapping we get the Raman tweezers that can be used to study the behaviour of entire cells simultaneously. Advantages Although another vibrational spectroscopy technique, infrared spectroscopy (IR), is more sensitive than Raman, it does not work well for aqueous solutions since it suffers from large water absorption effects. Raman does not suffer from these absorption effects and needs little or no sample preparation. It also has the added advantage that the spectra are generally unaffected by temperature changes, and that the concentration of the particular species is directly proportional to the intensity of spectral features shown. Raman gives an objective and accurate result reducing the time delay for receiving diagnosis and does not require chemicals to be added to samples. This was a contribution from Kirsty Scott, one of our undergraduate project students.
亲生儿子如是说：物理学家拉曼是个大骗子 2011.09.27 首先声明，这篇是八卦。 2011年9月19-23日，是所谓的National Postdoc Appreciation Week。PNNL实验室在今天下午举行了个小活动，百来个博士后和一些研究人员有个小聚会，吃吃点心，喝喝啤酒之类。 National Postdoc Appreciation Week网页链接： http://www.nationalpostdoc.org/meetings-and-events/appreciation 聚会的时候和一位做理论的印度同事聊天，他又给讲了些印度物理学家Raman的离奇故事，觉得有必要把它们写下来以免忘记。 这位同事的故事虽然离奇，但都是可信的。这不仅因为他是一位严谨的科学家，而且还因为他的外公是Raman的小舅子，也就是说Raman的太太是他的舅姑婆，而且他外公还是印度比较著名的生物学家。他说当年他外公因为他父亲不是做学问的人而反对他父母结婚，还是Raman三言两语说服了他外公同意这门婚事。所以Raman生前和他父亲的关系还相当不错，他父亲经常到Raman家走动，陪Raman散步和聊天。只是他太小，如果不是在Raman去世后才出生，也就是根本不记得见过Raman本人这事儿。 维基百科C.V. Raman介绍链接：http://en.wikipedia.org/wiki/C._V._Raman 同事说他记得三十多年前他还是小孩的时候，有位衣衫褴褛的人来他家敲门。他母亲开门后却没认出是谁，这人于是用流利的英文说到：“连我也不认得了吗？还真以为我是叫花子哪？”在印度叫花子是不会说流利的英文的。他妈妈听声音才认出来是自己的表兄，印度大物理学家Raman的大儿子Chandrasekhar。 同事说，Raman的大儿子Chandrasekhar之前本来是个非常优秀的律师，一表人才，优秀的演说家，奋斗下去完全有机会成为未来的印度总检察长之类的人物。可是Raman本人却坚决认为律师是个不正当的职业，而且更绝的是还因为这些事情跟他断绝了父子关系（disownedhim）。因为Raman在印度社会是如此重要的人物，而且印度社会又重视门阀和种姓，这样Chandrasekhar在社会上就没法继续混下去了，后来的命运也很悲惨。深受打击之下，他非常愤恨自己的父亲，逢人就说他父亲是世界上最大的骗子，说他相信Raman的那个1930年的Nobel物理学奖根本就应该是属于Raman的学生Krishnan，因为他第一个观察到了微弱的Raman散射谱线。 同事说他父亲曾经跟他的表兄解释过很多次，Krishnan作为Raman的学生或者助手，即使是第一个观察到了Raman谱线，也并不一定就是发现和理解这个现象的最重要的人。况且，Krishnan也没有声称自己才是最应该获得这项Nobel奖。可是Chandrasekhar就是不服，坚决声称他父亲是世界上最大的大骗子。 Nobel网站Raman关于Raman现象的诺贝尔演讲内容链接： http://www.nobelprize.org/nobel_prizes/physics/laureates/1930/raman-lecture.pdf （抱歉，您要是上不了Nobel网站，不要怪我。） 我自己因为做超快界面非线性光谱学的原因，最近也在顺便做一些关于受激Raman光谱的研究。尽管很长时间以来也读过不少关于各种各样的Raman光谱研究的论文，又有一位印度师兄是印度加尔各答Raman发现以他的名字命名的Raman现象的Indian Association for the Cultivation of Science的物理化学系的掌门，但实话实说，自己以前还真没太注意关于Raman的故事，直到碰到Raman的这位后辈亲戚。他的办公室和我的办公室在同一条走廊上，相距不过十米之遥。 Indian Association for the Cultivation of Science网页上的历史介绍： http://www.iacs.res.in/iacs_history.html 另外一件有意思的事情，是Raman的亲侄子Subrahmanyan Chandrasekhar于1983年获得诺贝物理学奖。以前看过Chandrasekhar的自传，发现他也对他的这位亲叔叔很有意见，而他妈妈最大的愿望就是自己的儿子在Raman活着的时候也获得诺贝尔物理学奖，免得Raman老是不待见他们这家人。因为对Raman有意见，Chandrasekhar选择根本不回印度，也很少和印度科学界打交道。很不幸，Raman于1970年去世，而Chandrasekhar在25岁左右就做出了令他获得Nobel物理学奖的工作，却因为当年爱丁顿的捣乱，他在1983年73岁时才获得Nobel奖。所以，Chandrasekhar终于没有让他妈妈如愿地在他的亲叔叔Raman面前扬眉吐气。 维基百科上Subrahmanyan Chandrasekhar的介绍链接： http://en.wikipedia.org/wiki/Subrahmanyan_Chandrasekhar Chandrasekhar的自传《孤独的科学之路》信息链接： http://book.douban.com/subject/1970216/ 对于Raman是不是大骗子这个问题，我的答案当然是：不是。尽管连Raman的亲儿子也坚持说是。 另外，用Chandrasekhar的学生杨振宁先生的所谓美与物理学的标准来看，Raman效应如果换成Krishnan效应，说起来太拗口，写起来也不简便，肯定是件不美的事情。 当然，前些年王朔同学对于杨振宁的美学标准很有意见，专门写了一本自传体小说《看上去很美》加以驳斥。 这是后话。
标签: raman
