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小木虫论坛-学术科研互动平台 » 计算模拟区 » 量子化学 » Gaussian » 该物质是对称结构，计算结果却是HOMO在左，LUMO在右。
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Illusionist

银虫 (正式写手)

[求助] 该物质是对称结构，计算结果却是HOMO在左，LUMO在右。

安装g09说明书，计算荧光光谱的方法算了一遍。

又有直接使用
# opt freq td=(nstates=6,root=1) b3lyp/6-31+g(d,p)
scrf=(solvent=n,n-dimethylformamide) geom=connectivity
然后SP算了一遍。

结果都是一样的。
该物质是对称结构，在DMF溶剂中计算，结果却是HOMO在左，LUMO在右，不再对称了。


是溶剂选择的模型有问题
还是什么？

新手，求教！
不胜感激。

（不方便上图，抱歉）
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1楼 2011-12-03 20:56:56
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Illusionist

银虫 (正式写手)
按照说明书上计算，到第四步的时候，没有使用OPT=RCFC，而直接使用OPT。因为使用OPT=RCFC无法进行。这一步之前，看的HOMO，LUMO
都是对称的·。
Step 1: Ground state geometry optimization and frequencies (equilibrium solvation). This is a standard Opt Freq calculation on the ground state including PCM equilibrium solvation.

%chk=01-ac
# B3LYP/6-31+G(d,p) Opt Freq SCRF=(Solvent=Ethanol)

Acetaldehyde ground state

0 1
C
C,1,RA
X,2,1.,1,A
O,2,RB,3,A,1,180.,0
X,1,1.,2,90.,3,0.,0
H,1,R1,2,A1,5,0.,0
H,1,R23,2,A23,5,B23,0
H,1,R23,2,A23,5,-B23,0
H,2,R4,1,A4,3,180.,0

RA=1.53643
RB=1.21718
R1=1.08516
R23=1.08688
R4=1.10433
A=62.1511
A1=110.51212
A23=109.88119
A4=114.26114
B23=120.56468
Step 2: Vertical excitation with linear response solvation. 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 solvation calculation. In this case, we see that the n->π* state is the first excited state. Next, we will use the state-specific method to produce a better description of the vertical excitation step.

%chk=02-ac
# B3LYP/6-31+G(d,p) TD=NStates=6 SCRF=(Solvent=Ethanol)
  Geom=Check Guess=Read

Acetaldehyde: linear response vertical excited states

0 1
Step 3: State-specific solvation of the vertical excitation. This will require 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. Second, the actual state-specific calculation is done, reading in the necessary information for non-equilibrium solvation using NonEq=read.

%chk=03-ac
# B3LYP/6-31+G(d,p) SCRF=(Solvent=Ethanol,Read)
  Geom=Check Guess=Read

Acetaldehyde: prepare for state-specific non-eq solvation
by saving the solvent reaction field from the ground state

0 1

NonEq=write

--link1--
%chk=03-ac
# B3LYP/6-31+G(d,p) TD(NStates=6,Root=1)
  SCRF=(Solvent=Ethanol,ExternalIteration,Read)
  Geom=Check Guess=Read

Acetaldehyde: read non-eq solvation from ground state and
compute energy of the first excited with the state-specific method

0 1

NonEq=read
Step 4: Relaxation of the excited state geometry. Next, we perform a TD-DFT geometry optimization, with equilibrium, linear response solvation, in order to find the minimum energy point on the excited state potential energy surface. Since this is a TD-DFT optimization, the program defaults to equilibrium solvation. As is typical of such cases, the molecule has a plane of symmetry in the ground state but the symmetry is broken in the excited state, so the ground state geometry is perturbed slightly to break symmetry at the start of the optimization.

%chk=04-ac
# B3LYP/6-31+G(d,p) TD=(Read,NStates=6,Root=1) SCRF=(Solvent=Ethanol)
  Geom=Modify Guess=Read Opt=RCFC

Acetaldehyde: excited state opt
Modify geometry to break Cs symmetry
since first excited state is A"

0 1

4 1 2 3 10.0
5 1 2 7 -50.0
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7楼2011-12-04 14:09:30
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tiaozaoququ

木虫 (著名写手)

【答案】应助回帖

Illusionist(金币+1): 2011-12-04 13:52:08
本人碰到同样的问题，关注一下
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再牛逼的选择也需要更傻逼的坚持
2楼2011-12-04 09:12:09
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Illusionist

银虫 (正式写手)
引用回帖:
2楼: Originally posted by tiaozaoququ at 2011-12-04 09:12:09:
本人碰到同样的问题，关注一下

是不是模型的问题？
把DMF溶剂的极性指向的随机分布变成了单一方向造成的啊··
求牛哥哥解答啊···
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3楼2011-12-04 10:52:20
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Illusionist

银虫 (正式写手)
Illusionist: 回帖置顶 2011-12-04 14:04:30
=================================
Model                : PCM.
Atomic radii         : UFF (Universal Force Field).
Polarization charges : Total charges.
Charge compensation  : None.
Solution method      : Matrix inversion.
Cavity type          : Scaled VdW (van der Waals Surface) (Alpha=1.100).
Cavity algorithm     : GePol (No added spheres)
                        Default sphere list used, NSphG=   56.
                        Lebedev-Laikov grids with approx.  5.0 points / Ang**2.
                        Smoothing algorithm: Karplus/York (Gamma=1.0000).
                        Polarization charges: spherical gaussians, with
                                              point-specific exponents (IZeta= 3).
                        Self-potential: point-specific (ISelfS= 7).
                        Self-field    : sphere-specific E.n sum rule (ISelfD= 2).
1st derivatives      : Analytical E(r).r(x)/FMM algorithm (CHGder, D1EAlg=3).
                        Cavity 1st derivative terms included.
Solvent              : n,n-DiMethylFormamide, Eps=  37.219000 Eps(inf)=   2.046330
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4楼2011-12-04 11:53:15
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