Raman Spectrum of Nitrobenzenethiol on Silver Nanoparticles

This experiment gives experience with surface-enhanced Raman spectroscopy (SERS) and with synthesis of nanoparticles. Silver nanoparticles will be prepared in aqueous solution. Nitrobenzenethiol will be bonded to nanoparticle surfaces. Surface-enhanced Raman spectra willbe observed, changing over time. Quantum-chemical calculations will show enhanced vibrationalmodes at the atomic level.

Introduction

Raman spectroscopy measures the intensity of scattered, frequency-shifted light. The basic method is named after Chandrasekhara Venkata Raman of the University of Calcutta. In vibrational Raman spectroscopy, the type used in this experiment, the difference between the scattered light's frequency and the source light's frequency equals a molecular vibration frequency. The source is a laser, approximately monochromatic. The Raman spectrum is comparable to an infrared spectrum, although the selection rules that determine which vibrational

modes are active in a Raman spectrum differ from the rules for infrared spectra.1,2 Relative intensities of peaks also differ.

When a molecule is on a metal surface the intensities of somevibrational modes in its Raman spectrum are increased. Ramanspectroscopy benefiting from such enhancement is called "surface-enhanced Raman spectroscopy," SERS. Intensities may increase by

factors of 103 to 106 or even more.3 In this experiment, 4-nitrobenzenethiol molecules will be covalently bonded to silver

nanoparticles. SERS of 4-nitrobenzenethiol on silver4,5 nanoparticles have been observed previously, and will be observed in this experiment.

Vibration frequencies and their Raman intensities will be calculated using density functional theory in the GAMESS program running under WebMO. For simplicity, frequencies and intensities will be calculated for an isolated molecule, not for a molecule bonded to a silver nanoparticle. Some representation of the silver surface could be included but calculations would

be harder and much longer.6,7 The calculated Raman intensities will not reflect SERS enhancement but may help understand the vibrational modes observed in SERS.

NBTsers.odt 1

Figure 1: 4-nitrobenzenethiol

Theory

The intensity, I, of a Raman transition is approximately proportional to the intensity of the laser

source and to the polarizability of the molecule.8

I ≈8πωL

4

9 c4I L ∑

i , jαi , j

2 (1)

In equation 1, ωL is the laser frequency and c is the speed of light. The intensity of the laser's

electric field at the molecule's location is IL. The matrix αi,j is the polarizability of the molecule; i

and j range over the x, y and z directions. Polarizability depends on the state of the molecule, and so on vibration frequency ω.

Surface enhancement is due to electromagnetic effects and molecular ("chemical") effects.8,9 Theelectromagnetic effect enters the local intensity, IL. In a vacuum, IL would equal the laser's output

intensity. A metal surface can greatly increase IL at molecules on the surface. The increase

depends on the shape of the surface and the nature of the surrounding solution. It is likely to be

largest perpendicular to the surface, and it is enhanced at contacts between nanoparticles.10 The electromagnetic effect may enhance especially modes in which atoms vibrate perpendicular to thesurface.

Chemical enhancement is described by the polarizability, which depends on the resonant

vibrational mode. Depending on the mode, αi , j2 may be enhanced by interaction with the

surface, interaction that has been described as electron transfer into vacant orbitals of the adsorbed molecules. Although which modes will be enhanced chemically is not easily predicted, spectra show that some modes are enhanced more than others.

At least in some cases, if a planar Raman-scattering molecule is perpendicular to a silver surface, in-plane vibrational peaks are preferentially surface-enhanced. Nitrobenzenethiol is planar. When it is bonded by its sulfur atom to silver the molecule's plane is approximately perpendicular to thesilver surface. It is expected, then, that in-plane vibrations of nitrobenzenethiol will be most enhanced in SERS. In-plane modes are of symmetry A' in the Cs symmetry group; A'' modes are

out-of-plane vibrations. For that reason, A'' vibrations calculated quantum-mechanically can be disregarded.

Quantum-chemical calculations of Raman intensities use polarizabilities, αi,j, for every vibration

frequency, ω. A conceptually useful expression comes from perturbation theory.

αi , j (ω)≈∑g , e [

⟨ g|μi|e ⟩ ⟨e|μ j|g ⟩

E e − E s − ℏω ] (2)

Cartesian directions x, y and z are represented by i and j. The initial ("ground") state is labeled

NBTsers.odt 2

"g"; the final ("excited") state "e". The operator μi is the dipole-moment operator. The notation

⟨ g|μi|e ⟩ stands for the product of the ground-state wave function, μi, and the excited-state wave

function, integrated over all space. The product ℏω is one quantum of vibrational energy. The quantum-mechanical calculation requires vibration frequencies, ω, which come from the "Hessian" matrix.

Hess Ii , Jj = ( ∂2 E

∂ q I ,i∂ qJ , j ) (3)

The upper-case I and J run over all atoms in the molecule. Lower-case i and j are, as above,

Cartesian directions x, y and z. Displacement ∂ qI ,i is an infinitesimal displacement of atom I

along coordinate i. The derivative is the second derivative of the total electronic energy. From the

Hessian, the dynamical matrix is easily calculated: D Ii , Jj=(M I M J )−1/2Hess Ii , Jj , where MI is

the mass of atom I. Eigenvalues of the dynamical matrix are the vibration frequencies ω that enter the calculation of Raman spectra.

The GAMESS quantum-chemical program calculates Raman intensities not from equation 1, but rather from expectation values of the derivatives of the polarizability with respect to vibrational

normal modes.11 The polarizability matrix elements are themselves calculated from second

derivatives of the total electronic energy with respect to an external electric field.12 Overall, third

derivatives of total energy are required for Raman intensities.12,13 Regardless of the method, calculating Raman intensities is rather difficult. The calculation will be faster by a factor of three or so if a pre-computed Hessian matrix is supplied. For that reason, adding the pre-computed Hessian to a GAMESS input file is part of the procedure below.

NBTsers.odt 3

The DeltaNu Raman Instrument

Raman spectra will be taken with the Advantage 200A Ramaninstrument. It was made by DeltaNu; more recently it is sold bySciAps, Inc. The instrument's light source is a 3mW 633-nmhelium-neon laser. The department has two sample holders: theliquid cell holder in Figure 2 and an xyz stage.

Begin by recording a spectrum of a sample ofpoly(methylmethacrylate) (PMMA) or cyclohexane. Experimentwith these settings:

• averaging (signal to noise increases as the square root)• collection time (1 second is default, longer is better)• baseline correction (a software correction on this instrument)

The reference spectrum is recorded internally. You might set it to be recorded every eight spectra.To prepare a spectrum to include in a report, save the display in an ascii ("prn") file. Ascii files can readily be imported into a spreadsheet for graphing. The spectrum in Figure 3 was prepared in that way.

If a spectrum is to be re-opened using the DeltaNu software, then save in the ".dnu" format, which saves more complete information.

ReagentsAgNO3 1.0×10-3 M aqueous solution (18 mg AgNO3 in 100 mL water)

Hazard: AgNO3 is a strong oxidizer. It burns on contact with skin or eyes.

sodium citrate dihydrate 1% aqueous CAS 6132-04-3The solution was made by dissolving 0.2 g sodium citrate dihydrate in 20 mL water.Sodium citrate dihydrate is not hazardous.

NaCl 0.1 M aqueousThe solution was made by dissolving 0.585 g NaCl in 100 mL water. Sodium chloride is not hazardous.

4-nitrobenzenethiol (NBT), HS(C6H4)NO2 1.0×10-4 M aqueous CAS 1849-36-1, 155.2 g/mol.

The solution can be made by dissolving 1.0 mg NBT in 65 mL water. The solution is nearly saturated.Hazard: 4-nitrobenzenethiol irritates eyes, skin and respiratory system. Do not ingest.

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Figure 3: Raman spectrum of liquid cyclohexane.

Procedure

make silver nanoparticles

The following instructions were adapted from methods of Brandt4 and Lee.14

Prepare a beaker in which to make silver nanoparticles. It is important that the beaker and stirbar be clean of old nitrobenzenethiol. Scrub with lab soap and a brush. Then rinse with methanol. If the stir bar has a central ridge, use a cotton swab to clean around it.

Dissolve 18 mg AgNO3 in 100 mL water in a clean beaker. Add a stir bar. Cover with a watch

glass. Heat and stir on a hot plate until the solution boils. Then add 2 mL of 1% sodium

citrate solution. (On the Cimarac stirring hot plate, the 330oC setting brought the solution to a

boil, the 260oC setting maintained boiling.) Boil vigorously for one hour. The solution will change color, eventually turning brown-gray with nanoparticles. Metallic silver may deposit on the beaker as silver ions are reduced.

Cool the solution to near room temperature.

make the NBT solution while the silver solution boils

Dissolve 1.0 mg NBT in 65 mL water. Use a stir bar and stir plate to aid dissolution.

prepare the Raman spectrometer There will be time while boiling the silver solution and stirring the NBT solution.

Turn on the Raman spectrometer and start its software if it is not already on. Set resolution to medium. Turn baseline correction on.

Use a vial of cyclohexane as a reference compound. Adjust the vial's position and practice collecting spectra until your spectrum shows the peaks present in Figure 3.Put a piece of paper or tape on the xyz stage and mark the position of the vial. Take all remaining spectra with a vial in that position. Save the spectrum as an ASCII ("*.prn") file. Produce a spectrumfrom the file and include it in your report.

After recording a spectrum of a reference compound, set the software to display Raman spectra from 600 to 1800 cm-1. To scale the x (wavenumber) axis, left-click on the graph icon( ), unselect "autoscale x," then type x start and end values (600 and 1800) directly on the graph axis. Most spectra should be taken over long times because signals are weak and noisy. Suitable settings are 16 scans, each 4 seconds long. Set the software to display the average of the scans. (I.e., Number of Spectra to Acquire=16, Integration Time=4, Display=average.)

Samples will be in glass vials. There may be peaks at approximately 1660, 1700 and 1760

NBTsers.odt 5

cm-1 from the glass. Record and save a spectrum of an empty glass vial.

Prepare the NBT control sample as described below: 2.3 mL water, 0.7 mL NBT solution, and1.0 mL 0.1M NaCl solution. Record the Raman spectrum.

bond 4-nitrobenzenethiol to silver nanoparticles as soon as the silver solution is ready

Table 1. four samples (the experiment will be run in duplicate)

components sample 1 sample 2 Ag control NBT control

Ag nanoparticles

2.3 mL 2.3 mL 2.3 mL 2.3 mL water

NBT 0.7 mL 0.7 mL 0.7 mL water 0.7 mL

• For each sample place 2.3 mL of the silver nanoparticle solution (or water, for the NBT control) in a test tube or (if a vortex mixer is available) a centrifuge tube.

• Add 0.7 mL of either the NBT solution or (for the Ag control) water. When making samples 1 and 2, add NBT solution dropwise while vortexing (or shaking, if there is no vortex mixer) the silver solution. Dropwise addition is to disperse the NBT molecules among the siver nanoparticles.

• Mix both sample 1 and sample 2 thoroughly by shaking or vortexing for 10 minutes.• To each sample (to all four) add 1 mL 0.1M NaCl.• Mix briefly by shaking or vortexing.• Transfer to a Raman sample bottle (blue-top 4-mL vial) or tube (if the liquid sample

holder is to be used).

record uv-visible spectra of the nanoparticles

Scan the baseline with a sample of water from 350 to 750 nm.

Fill a square cuvette with the "Ag control" solution, diluted as necessary (approximately 10:1) to keep the spectrum on scale. Between recording Raman spectra, record uv-visible spectra of the Ag control solution. A peak at 410 nm to 430 nm may be observed, and may

change over time.15,16 Record a spectrum every ten minutes until the spectrum does not change. (If from the first, the spectrum does not change, then two spectra suffice.)

record Raman spectrum of the nanoparticles

Record the Raman spectrum of the "Ag control" solution. This spectrum could be featureless noise or it could contain peaks. If there are peaks, those must be considered when interpreting later spectra that are taken of solutions containing both NBT and nanoparticles. Also, if there are peaks, consider the possibility that the silver control solution contains some NBT; it may not be so but it is worth considering.

NBTsers.odt 6

normal Raman spectra

Record the Raman spectrum of the NBT stock solution. This spectrum will either show peaksof non-surface-enhanced scattering or it will show that the normal spectrum is too weak to beobserved.

surface-enhanced Raman spectra

Periodically record spectra of both samples (i.e., of sample 1 and sample 2). A suggested schedule is 16-scan averages of 4-second scans (so, 64 seconds per spectrum) taken at 10-minute intervals for one hour. Shake or vortex samples briefly between spectra to prevent settling.

DFT calculations of vibrational modes corresponding to intense peaks.

Including the silver nanoparticle in quantum calculations is possible but not in the time available in this course, so calculations will be for the isolated 4-nitrobenzenethiol molecule. We will use density functional theory (DFT) to calculate Raman frequencies and intensities. That is a difficultcalculation, so to keep the time short, the previously-optimized geometry, the Hessian matrix, andthe gradient will be provided. Use the pre-optimized NBT molecule that is provided on the Build/

Fragment/OptimizedMolecules menu. The PBE (Perdew-Burke-Ernzerhof) functional,17 which is a gradient-corrected pure functional (a "GGA"), will be used. To keep the calculation fast (approximately one-half hour), the medium-size 6-31G(d) basis set will be used. Because the provided geometry, Hessian and gradient were calculated with functional PBE and basis set 6-31G(d) those aspects of the calculation cannot be changed when calculating Raman frequencies and intensities. The molecule's lowest-energy geometry is planar. Its symmetry group is Cs, meaning in this case

that all atoms of the molecule are in one plane. For the GAMESS program, that plane must be the(x,y) plane. The optimized geometry provided (under Build/Fragment) is already in the (x,y) plane and has Cs symmetry.

To calculate Raman frequencies and intensities, the GAMESS-input RUNTYP must be "RAMAN." That is not on WebMO's menu of run types, so choose "Other" and type it in. Doing a Raman calculation requires additional manual adjustments to the input file.

• The $DATA section starts with "Cs," which will cause GAMESS to label each calculated vibration frequencies with its symmetry type. The surface-enhanced Raman modes for this molecule will be of A' type; A" modes can be neglected. Following the "Cs" line there

NBTsers.odt 7

must be a blank line. Atoms and their coordinates follow the blank line. In case of difficulty, examine the sample input file in the appendix that follows the references in this document.

• To get the Hessian and Gradient from the "NBTpbeGradHess.txt" file, simply open it witha text editor, select and copy all. The file can be found in the "lab instructions" section of the class web site.

• Following the $DATA ... $END section in the GAMESS input file, paste the $GRAD and $HESS groups into the WebMO job preview.

• In the $CONTRL group, insert the command MAXIT=50. This allows the SCF iteration to take up to 50 steps when calculating the wavefunction. The default number allowed, 30, may not be enough.

• If there is not already a $SYSTEM group, insert the following line to request extra memory. $SYSTEM MWORDS=128 $END

• In the $SCF group, specify the "direct" SCF method (i.e., calculating integrals as needed rather than reading them from disk) and a tightened convergence criterion (because Raman intensities depend on the third derivative of energy and so are sensitive to small

errors). The same convergence criterion, 10-6, was used in optimizing coordinates and calculating the Hessian. The SCF group can follow the BASIS group. $SCF DIRSCF=.TRUE. CONV=1.0D-6 $END

After the Raman job runs (It takes about half an hour.) open the raw output and look near the end for "FREQUENCIES." There will be a long list of vibrational modes. For each, the frequency (in

cm-1), the symmetry (A' or A''), the Raman activity (also called intensity), and other information will be shown.

Analysis of Results

General note: include all spectra in your lab report.

Address the following points in your report:

• Does the glass vial itself exhibit Raman peaks? If so, are they also observed in spectra of silver and of NBT with silver?

• Does the uv-visible spectrum of the Ag control show evidence of silver nanoparticles? Does it change over time?

• Does the "Ag control" sample have a Raman spectrum? Do nanoparticles contribute to theRaman background?

• Did you see a non-surface-enhanced (i.e., "normal") Raman spectrum, with the "NBT control" sample? If so, note the peak frequencies and intensities.

NBTsers.odt 8

• At what wavenumbers are surface-enhanced Raman peaks? Do spectra from sample 1 andsample 2 differ? Do they change with time? If there is time dependence, plot intensity versus time for at least one peak in both spectra.

• If samples 1 and 2 gave similar spectra, average them for the rest of the analysis. The average can simply be done in the spreadsheet. Show the averaged spectrum in your report.

• Published SERS of NBT have peaks near 855, 1110, 1345 and 1570 cm-1, plus other

locations. [Brandt4 Fig. 1, Kim5 Fig. 1b, Ren18 Fig. 2, Thomas9 Table 2 and Fig. 5, You19 Fig. 2] Compare your SERS to a published spectrum.

• An intense peak in surface-enhanced Raman spectra of NBT solutions and normal Raman spectra of solid NBT has been observed in the range 1325 to 1343 cm-1. A DFT calculation that used the B3LYP functional identified that peak at 1276 cm-1.20 At what frequency does this vibration appear in your surface-enhanced spectra? Find the mode in your GAMESS Raman output. It will have a large calculated Raman intensity and will be of A' symmetry. Use MacMolPlt to display the mode and to animate it. Include an arrow-representation of the mode in your report. The mode has been described as "NO2 symmetric stretch." Is that what you observe?

• Another intense peak has been observed in the range 1570 - 1577 cm-1. DFT B3LYP placed it at 1567 cm-1.20 Find the mode in your GAMESS Raman output, where it should have A' symmetry and a large calculated Raman intensity. Use MacMolPlt to display the mode and to animate it. Include an arrow-representation of the mode in your report. What atoms move in this mode? Describe the mode .

• NBT has been shown to dimerize on silver nanoparticles.4,5 The product, the dimer p,p'-

dimercaptoazobenzene,4 has Raman peaks at 1140 and 1435 cm-1. If your Raman spectra show peaks at those locations and the peaks grow with time then plot intensity of one or both versus time.

• Make a hypothesis about why there is time dependence in the Raman spectra (if there wastime dependence) and propose an experiment that would help test the hypothesis.

NBTsers.odt 9

AcknowledgmentThanks to Professor Renee Frontiera of the University of Minnesota Twin Cities for suggesting

this experiment during a seminar visit.

References1. Cooksy, Andrew, Physical Chemistry: Quantum Chemistry and Molecular Interactions, Pearson:

Upper Saddle River, New Jersey: 2014. Raman spectroscopy, including selection rules and surface enhancement, is discussed in Section 3 of Chapter 6.

2. Atkins, Peter; de Paula, Julio; Keeler, James, Physical Chemistry, 11th ed., Oxford University Press: Oxford, 2018.

3. Chowdhurry, Joydeep, "How the Charge Transfer (CT) Contributions Influence the SERS Spectra of Molecules. A Retrospective from the View of Albrecht’s A and Herzberg-Teller Contributions," Applied Spectroscopy Reviews, 2015, 50, 240-260. DOI: 10.1080/05704928.2014.942815.

4. Brandt, Nathaniel C.; Keller, Emily L.; Frontiera, Renee R. "Ultrafast surface-enhanced Raman probing of the role of hot electrons in plasmon-driven chemistry," Journal of Physical Chemistry Letters, 2016, 7, 3179-3185. DOI: 10.1021/acs.jpclett.6b01453. This article describes nanoparticle preparation and shows SERS spectra of 4-nitrobenzenethiol. The focus of the article is kinetics of dimerization.

5. Kim, Kwan; Coi, Jeong-Yong; Shin, Kuan Soo, "Surface-enhanced Raman scattering of 4-nitrobenzenethiol and 4-aminobenzenethiol on silver in icy environments at liquid nitrogen temperature," Journal of Physical Chemistry C, 2014, 118, 11397-11403. Nitrobenzenethiol reaction kinetics by SERS at low temperature, including dependence on wavelength of the source.

6. Pan, Wen-Xiao; Lai, Yong-Chao; Wang, Ruo-Xi; Zhang, Dong-Ju; Zhan, Jin-Hua, "Theoretical elucidation of the origin of surface-enhanced Raman spectra of PCB52 adsorbed on silver substrate," Journal of Raman Spectroscopy, 2014, 45, 64-61.DOI: 10.1002/jrs.4421

7. Maiti, Nandita; Chadha, Ridhima; Das, Abhishek; Kapoor, Sudhir, "Surface selective binding of 2,5-dimercapto-1,2,3,4-thiadiazole (DMTD) on silver and gold nanoparticles: a Raman and DFT study," RSC Advances, 2016, 6, 62529-62539. DOI:10.1039/c6ra10404e

8. Lombardi, John R.; Birke, Ronald L., "A unified approach to surface-enhanced Raman spectroscopy," Journal of Physical Chemistry C, 2008, 112, 5605-5617. DOI: 10.1021/jp800167v

9. Thomas, Martin; Mühlig, Stefan; Deckert-Gaudig, Tanja; Rockstuhl, Carsten; Deckert, Volker; Marquetand, Philipp, "Distinguishing chemical and electromagnetic enhancement in surface-enhancedRaman spectra: The case of para-nitrothiophenol," Journal of Raman Spectroscopy, 2013, 44, 1497-1505. DOI: 10.1002/jrs.4377. Spectra, DFT calculations, and interpretations for SERS of nitrobenzenethiol.

10. Michaels, Amy M.; Jiang, Jiang; Brus, Louis, "Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single Rhodamine 6G molecules," Journal of Physical Chemistry B, 2000, 104, 11965 - 11971. DOI: 10.1021/jp0025476.

11. Jensen, Frank, Introduction to Computational Chemistry, 2nd ed., Wiley: New York, 2007, page 319.

NBTsers.odt 10

12. Hu, Wei; Duan, Sai; Luo, Yi, "Theoretical modeling of surface and tip-enhanced Raman spectroscopies," WIREs Computational Molecular Science, 2017, 7, 1-15. DOI: 10.1002/wcms.1293.

13. Halls, Mathew D.; Schlegel, H. Bernard, "Comparison study of the prediction of Raman intensities using electron structure methods," Journal of Chemical Physics, 1999, 111(19), 8819-8824. DOI: 10.1063/1.480228.

14. Lee, P. C.; Meisel, D. "Adsorption and surface-enhanced Raman of dyes on silver and gold sols," Journal of Physical Chemistry, 1982, 86(17), 3391-3395. Synthesis method c.

15. Dong, Xinyi; Ji, Xiaohui; Wu, Hongli; Zhao, Lili; Li, Jun; Yang, Wensheng, "Shape control of silver nanoparticles by stepwise citrate reduction," Journal of Physical Chemistry C, 2009, 113(16), 6573-6576. DOI: 10.1021/jp900775b.

16. Pillai, Zeena S.; Kamat, Prashant V., "What factors control the size and shape of silver nanoparticles in the citrate ion reduction method?" Journal of Physical Chemistry B, 2004, 108(3), 945-951. DOI: 10.1021/mp037018r. Figure 1.

17. Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias, "Generalized gradient approximation made simple," Physical Review Letters, 1996, 77(18), 3865-3868.

18. Ren, Xiaoqian; Tan, Enzhong; Lang, Xiufeng; You, Tingting; Jiang, Li; Zhang, Hongyan; Yin, Penggang; Guo, Yin, "Observing reduction of 4-nitrobenzenethiol on gold nanoparticles in situ using surface-enhanced Raman spectroscopy," Physical Chemistry Chemical Physics, 2013, 15, 14196-14201. DOI: 10.1039/c3p51385h. SERS of nitrobenzenethiol and a reaction product on gold nanoparticles.

19. You, Tingting.; Jiang, Li; Yin, Penggang; Shang, Yang; Zhang, Donfeng; Guo, Lin; Yang, Shihe, "Direct observation of p,p'-dimercaptoazobenzene produced from p-aminothiophenol and p-nitrothiophenol on Cu2O nanoparticles by surface-enhanced Raman spectroscopy," Journal of Raman

Spectroscopy, 2014, 45, 7-14. DOI:10.1002/jrs.4411. SERS of nitrobenzenethiol and a reaction product on copper oxide nanoparticles.

20. Skadtchenko, B. O.; Aroca, R. "Surface-enhanced Raman scattering of p-nitrothiophenol. Molecular vibrations of its silver salt and the surface complex formed on silver islands and colloids," Spectrochimica Acta Part A, 2001, 57, 1009-1016.

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Appendix: GAMESS input file from a WebMO run.

$CONTRL SCFTYP= RHF RUNTYP=Raman DFTTYP=PBE ICHARG=0 MULT=1 COORD=UNIQUE MAXIT=50 $END $SYSTEM MWORDS=100 $END $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=1 $END $SCF DIRSCF=.TRUE. CONV=1.0D-6 $END $DATA 4NBT PBE 6-31g(d) Cs Raman Cs

C 6.0 -0.9750064172 1.2364509094 0.0 C 6.0 -1.6929610546 0.0211809861 0.0 C 6.0 -0.9897927616 -1.2042602351 0.0 C 6.0 0.4043462548 -1.2162166417 0.0 C 6.0 1.0978750870 0.0016504385 0.0 C 6.0 0.4206966563 1.2277295944 0.0 H 1.0 0.9963518729 2.1559358122 0.0 N 7.0 2.5676668056 -0.0067721425 0.0 O 8.0 3.1487603260 1.0919269580 0.0 O 8.0 3.1362837886 -1.1118172497 0.0 H 1.0 0.9664003977 -2.1523898771 0.0 H 1.0 -1.5394470457 -2.1505758611 0.0 S 16.0 -3.4654200979 -0.0581041990 0.0 H 1.0 -3.6877330341 1.2825878964 0.0 H 1.0 -1.5063821712 2.1933370925 0.0 $END $GRAD E= -834.2691397581 GMAX= 0.0000531 GRMS= 0.0000184C 6. -2.6809381750E-05 4.4057845124E-05 0.0000000000E+00C 6. -4.8306519557E-05 -7.9921817597E-06 0.0000000000E+00C 6. -1.0573560085E-05 -2.5905250055E-05 0.0000000000E+00C 6. 2.3882860155E-05 -3.2241309468E-05 0.0000000000E+00C 6. 5.3122996256E-05 -1.0635813497E-05 0.0000000000E+00C 6. 3.5782377308E-05 1.5042514549E-05 0.0000000000E+00H 1. 2.3347319221E-06 -8.8638293620E-06 0.0000000000E+00N 7. -3.8576969358E-05 4.4164248225E-06 0.0000000000E+00O 8. -2.9001844247E-06 7.9296721970E-06 0.0000000000E+00O 8. -8.2259460003E-06 -6.5457522336E-06 0.0000000000E+00H 1. 7.6106979015E-06 2.0409124720E-05 0.0000000000E+00H 1. 4.7592337478E-07 3.7394817650E-06 0.0000000000E+00S 16. 9.3911141862E-06 2.3324717540E-05 0.0000000000E+00H 1. 1.7381910474E-06 -1.5224275326E-05 0.0000000000E+00H 1. 1.0536690247E-06 -1.1511369016E-05 0.0000000000E+00 $END $HESSENERGY IS -834.2691397581 E(NUC) IS 552.9871688304 1 1 6.68259489E-01-3.89974326E-02-1.26472150E-12-1.42464504E-01-5.59163860E-02 1 2-5.78851898E-13 4.94272025E-02-1.49078869E-02 2.92611462E-12-3.69958315E-02 1 3-2.38247273E-02 2.33410474E-12-3.32439239E-02 6.24058840E-02-1.33952170E-12 1 4-3.48510150E-01-2.50732410E-02-3.94382555E-12-1.06560026E-02 2.73169359E-03 1 5-7.25812707E-13 1.03070049E-02 4.61758313E-03 3.01996731E-12-1.07977097E-03 1 6-3.42246564E-03-1.29197588E-12-3.17921615E-03 1.49382388E-03 5.70837061E-11

..... Several pages were deleted to save space in this appendix.

45 8 3.80161774E-04 4.21623071E-12-2.98833198E-12-2.05857956E-03 2.10126359E-1345 9 6.97633784E-13 4.01908054E-04 5.87116737E-13-3.70688553E-13 2.17589197E-02 $END

NBTsers.odt 12

Note: COORD=ZMTMPC also works, but then the coordinates in the $DATA section must be internal ("Z-matrix") coordinates instead of Cartesian coordinates. Cartesian coordinates are shown in this appendix.