采用PCM模型计算溶液中的紫外吸收光谱The PCM method in Gaussian 09 includes an external iteration procedure whereby the program computes the energy in solution by making the solvent reaction field self-consistent with the solute electrostatic potential (the latter being generated from the computed electron density with the specified model chemistry).Step 1: Ground state geometry optimization and frequencies (equilibrium solvation平衡溶剂化：在电子结构不发生改变时，若分子几何结构发生变化则 溶剂也跟着变化). This is a standard Opt Freqcalculation on the ground state including PCM equilibrium solvation.获得溶剂中基态稳定几何结构，默认为Eq状态%chk=01-ac# B3LYP/6-31+G(d,p) Opt Freq SCRF=(Solvent=Ethanol)Acetaldehyde ground state0 1分子说明(请自行补充)Here is the energy of the ground state optimized geometry in solution:SCF Done: E(RB3LYP) = -153.851761719 A.U. after 1 cyclesStep 2: Vertical excitation with linear response solvation.默认为 Non-Eq 过程This is a TD-DFT calculation of the vertical excitation, therefore at the ground state equilibrium geometry, with the default solvation: linear response, non-equilibrium. We perform a single-point TD-DFT calculation, which defaults to non-equilibrium solvation. The results of this job will be used to identify which state or states are of interest and their ordering. These results give a reasonable description of the solvation of the excited state, but not quite as good as that from a state-specific solvationcalculation. In this case, we see that the n(产生第一谶发态的跃迁方式)isthe first excited state.Next, we will use the state-specific method to produce a betterdescription of the vertical excitation step.复制以上step1中的01-ac.chk,并将复制文件命名为02-ac.chk，然后执行如下操作计算紫 外跃迁吸收光谱。下边这个计算默认为non-equilibrium solvation。垂直激发默认为NonEq过 程，但此时没有使用EI%chk=02-ac# B3LYP/6-31+G(d,p) TD=NStates=6 SCRF=(Solvent=Ethanol)Geom=Check Guess=ReadAcetaldehyde: linear response vertical excited states0 1The vertical excitation (absorption) to first excited state from the non-equilibrium solvation linear response calculation:发生电子跃迁时，溶剂来不及运动，所以叫 做 non-equilibrium solvation linear responseExcited State 1:Singlet-A 4.3767 eV 283.28 nm f=0.0000 =0.000Thus, the ground state to first excited state absorption is at 283.28 nm, computed via the linear-response approach.Step 3: State-specific solvation of the vertical ThicWiatrbquire two job steps: first the ground state calculation is done, specifying NonEq=write in the PCM input section, in order to store the information about non-equilibrium solvation based on the ground state(之前基态优化的时候是 equilibrium solvation linear response 情 况下完成的，这里重新改用NonEq方法，并将信息保存下来).查得最后的能量数据为E(RB3LYP) = -153.851761719Second, the actual state-specific calculation is done, reading in the necessary information for non-equilibrium solvation using NonEq=read, and specifying the checkpoint file from Step2:这一步从step3的第一步中读取NonEq信息，并执行 激发态计算，获得垂直激发的能量。查得最后的能量数据为E(RB3LYP) = -153.850869764。同时会给出 After PCM corrections, the energy is -153.687679830 a.u.由于设定了 Root=1，所以只会给出第一激发态的如下详细信息：This state for optimization and/or second-order correction. Copying the excited state density for this state as the 1-particle RhoCI density .但不知道这个信息有什么用处。最后给出 的能量也许是第一激发态弛豫前的能量，而非基态能量.3.1与step 1相同，区别在于采用NonEq=Write保留了环境状态作为下一步NonEq 过程的状态3.2针对3.1的NonEq=Write环境，用NonEq=Read读取此环境。采用SCRF=EI 方法使得溶质的第一激发态(Root= 1指定为针对第一激发态)调整electron density 状态，达到与读取环境自洽的状态。注意，3.1起始几何结构与3.2终止几何结 构全同，没有改变。3.2的能量减去3.1的能量即为带有溶剂效应矫正后的紫外 吸收光谱。复制01-ac.chk文件，并将复制后文件重新命名为03-ac.chk。执行如下计算%chk=03-ac# B3LYP/6-31+G(d,p) SCRF=(Solvent=Ethanol,Read) Geom=Check Guess=ReadAcetaldehyde: prepare for state-specific non-eq solvation by saving the solvent reaction field from the ground state0 1NonEq=writelink1%chk=03-ac#P B3LYP/6-31+G(d,p) SCRF=(Solvent=Ethanol,ExternalIteration,Read) Geom=CheckGuess=Read TD(NStates=6,Root=1)Acetaldehyde: read non-eq solvation from ground state and compute energy of the first excited with the state-specific method0 1NonEq=readHere is the energy of first excited stateat the ground state optimized geometryfrom the non-equilibrium solvation state-specific calculation:After PCM corrections, the energy is -153.687679826 a.u.Subtracting this energy from the ground state energy (from step 1) gives the ground state to first excited state absorption including the state-specific solvation correction: at 277.69 nm.计算溶剂中的激发吸收光谱！Externaliteration方法但1方法）的大致含义是：不同于之前常用的标准方法（标准方法中计 算溶剂效应时先采用SCF方法获得初步结果，然后把溶剂效果当做微扰项叠加到体系中获 得体系性质），EI方法直接针对溶剂体系的MP2结果获得溶剂效果，让溶质自洽于环境溶剂。问题，若在3.2中，去除SCRF=EI关键词，则能量数值有多大变化，激发波长有多大变化？ 若能量数值和激发波长均不变，则表示对光谱结果数据没有影响，这样就不叫state-specific solvation correction 了。所以我想应该是变化了。若变化了，一次只能使用ROOT=N计算第N 个激发的具体波长，每次激发单独计算，这样很费事。但我们可以计算振动系数比较大的几 个紫外光谱就行了！并不是每个都要计算