Dear Emine,

Yes you can, However, the total charge is zero. Therefore, in line 4 of the input file you should type 0 for charge and 1 for multiplicity such as:

The charge distribution will be done by the program itself. You should not assign charges to the molecules atoms.

0      1

Hoping this will be helpful,

Rafik

Essenially, the quantum chemistry (Gaussian 09) itself should be able to figure out that the interaction between Na and Cl in NaCl (for example) is essentially ionic.  You should see covanent and ionic bonds as being two extremes, with a whole continuum of possibilities lying inbetween.  In short, NaCl has a very small amount of covalent interaction and H2O exhibits some degree of ionicity. Indeed, even in water, the OH bond has a far greater percentage of electrons on the O2- and maybe 10% present on the H+.  So with NaCl, what you will see is that most of the electron density likes on the Cl- and very little of it on the Na+.  This can be seen in the coefficients for the wave function at the highest most (electron) occupied orbitals. It might be easier to see these difference with a problem like HF, and LiF. 

Mrs Sas,

As I have understood from your question you would like to distinguish theoretically both the states shown as attachment as Mol-1 and Mol-2. You have written in fact the state Mol-2.

If yes, the input Gaussian files are shown below:

Mol-1:

%Chk=1.chk

# opt=(calcfc,gdiis) freq rb3pw91/6-31+g(d,p) scf=qc geom=connectivity

pop=minimal test

1

0 1

C

C 1 B1

O 1 B2 2 A1

C 1 B3 3 A2 2 D1

C 4 B4 1 A3 3 D2

C 2 B5 1 A4 3 D3

O 5 B6 4 A5 1 D4

C 6 B7 2 A6 1 D5

C 6 B8 2 A7 1 D6

C 4 B9 1 A8 3 D7

C 10 B10 4 A9 1 D8

C 10 B11 4 A10 1 D9

C 12 B12 10 A11 4 D10

O 8 B13 6 A12 2 D11

C 8 B14 6 A13 2 D12

C 9 B15 6 A14 2 D13

O 9 B16 6 A15 2 D14

C 16 B17 9 A16 6 D15

O 12 B18 10 A17 4 D16

C 11 B19 10 A18 4 D17

O 11 B20 10 A19 4 D18

C 13 B21 12 A20 10 D19

H 13 B22 12 A21 10 D20

H 14 B23 8 A22 6 D21

H 15 B24 8 A23 6 D22

H 16 B25 9 A24 6 D23

H 17 B26 9 A25 6 D24

H 18 B27 16 A26 9 D25

H 19 B28 12 A27 10 D26

H 20 B29 11 A28 10 D27

H 21 B30 11 A29 10 D28

H 22 B31 13 A30 12 D29

B1 1.47098380

B2 1.23081847

B3 1.47066067

B4 1.47096887

B5 1.43962580

B6 1.23064192

B7 1.42035599

B8 1.41953810

B9 1.43997397

B10 1.41981953

B11 1.41959417

B12 1.39550210

B13 1.35762376

B14 1.39483581

B15 1.39559492

B16 1.35754135

B17 1.39322672

B18 1.35756646

B19 1.39516591

B20 1.35757785

B21 1.39350365

B22 1.10249171

B23 0.97029870

B24 1.10251566

B25 1.10250024

B26 0.97035350

B27 1.10169238

B28 0.97034409

B29 1.10247842

B30 0.97030354

B31 1.10174153

A1 135.50161323

A2 135.48183350

A3 91.00114241

A4 134.44447158

A5 135.52522243

A6 120.50544678

A7 120.39763589

A8 134.44477886

A9 120.45055642

A10 120.43499980

A11 119.47292019

A12 122.46061654

A13 119.45699257

A14 119.49312205

A15 122.46880658

A16 121.50322051

A17 122.46259682

A18 119.46646085

A19 122.42398838

A20 121.50211414

A21 119.43174994

A22 108.74224016

A23 119.45177471

A24 119.41784128

A25 108.80678893

A26 120.53885259

A27 108.81538180

A28 119.44944507

A29 108.77750340

A30 120.53179297

D1 -179.93208502

D2 -179.81168020

D3 -0.81525646

D4 179.94404026

D5 -178.11212074

D6 1.65761251

D7 1.14236172

D8 -179.08954030

D9 1.19597034

D10 178.49662116

D11 -0.05265726

D12 179.18746375

D13 -179.51270409

D14 0.57796480

D15 0.16757991

D16 -0.62518084

D17 -178.98371494

D18 1.41757248

D19 0.73804634

D20 -179.17002297

D21 178.33195096

D22 -179.42808509

D23 -179.99018431

D24 179.67277212

D25 179.68427261

D26 178.56404142

D27 -179.98727307

D28 178.01267165

D29 -179.95855117

1 2 1.0 3 2.0 4 1.0

2 5 1.0 6 1.5

3

4 5 1.0 10 1.5

5 7 2.0

6 8 1.5 9 1.5

7

8 14 1.0 15 1.5

9 16 1.5 17 1.0

10 11 1.5 12 1.5

11 20 1.5 21 1.0

12 13 1.5 19 1.0

13 22 1.5 23 1.0

14 24 1.0

15 18 1.5 25 1.0

16 18 1.5 26 1.0

17 27 1.0

18 28 1.0

19 29 1.0

20 22 1.5 30 1.0

21 31 1.0

22 32 1.0

23

24

25

26

27

28

29

30

31

32

Mol-2:

%Chk=1a.chk

# opt=(calcfc,gdiis) freq rb3pw91/6-31+g(d,p) scf=qc geom=connectivity

pop=minimal test

1a

0 1

C

C 1 B1

O 1 B2 2 A1

C 1 B3 3 A2 2 D1

C 4 B4 1 A3 3 D2

C 2 B5 1 A4 3 D3

O 5 B6 4 A5 1 D4

C 6 B7 2 A6 1 D5

C 6 B8 2 A7 1 D6

C 4 B9 1 A8 3 D7

C 10 B10 4 A9 1 D8

C 10 B11 4 A10 1 D9

C 12 B12 10 A11 4 D10

O 8 B13 6 A12 2 D11

C 8 B14 6 A13 2 D12

C 9 B15 6 A14 2 D13

O 9 B16 6 A15 2 D14

C 16 B17 9 A16 6 D15

O 12 B18 10 A17 4 D16

C 11 B19 10 A18 4 D17

O 11 B20 10 A19 4 D18

C 20 B21 11 A20 10 D19

H 13 B22 12 A21 10 D20

H 14 B23 8 A22 6 D21

H 15 B24 8 A23 6 D22

H 16 B25 9 A24 6 D23

H 17 B26 9 A25 6 D24

H 18 B27 16 A26 9 D25

H 19 B28 12 A27 10 D26

H 20 B29 11 A28 10 D27

H 21 B30 11 A29 10 D28

H 22 B31 20 A30 11 D29

B1 1.39199441

B2 1.23079201

B3 1.39203224

B4 1.39354102

B5 1.33700036

B6 1.23058803

B7 1.42027336

B8 1.41945685

B9 1.33700465

B10 1.41974515

B11 1.41950794

B12 1.39545394

B13 1.35756957

B14 1.39473497

B15 1.39556122

B16 1.35753053

B17 1.39333236

B18 1.35756328

B19 1.39510707

B20 1.35755690

B21 1.39337819

B22 1.10241645

B23 0.97022668

B24 1.10245298

B25 1.10241067

B26 0.97033058

B27 1.10169410

B28 0.97030222

B29 1.10253479

B30 0.97022261

B31 1.10173499

A1 135.50248184

A2 135.48135495

A3 92.69800202

A4 134.44357345

A5 136.37937096

A6 120.50826173

A7 120.39597523

A8 135.92207482

A9 120.45419352

A10 120.43211955

A11 119.47241112

A12 122.45613357

A13 119.45717738

A14 119.49313961

A15 122.46684292

A16 121.49480896

A17 122.46333022

A18 119.46113601

A19 122.42002444

A20 121.52401566

A21 119.24833539

A22 107.99805198

A23 119.23362144

A24 119.24969723

A25 107.99892016

A26 120.54443493

A27 107.99720044

A28 119.23675264

A29 107.99959300

A30 120.53603779

D1 179.42620530

D2 179.25909723

D3 1.51161829

D4 -179.72309464

D5 -178.12533964

D6 2.46701279

D7 0.08332500

D8 -179.10718401

D9 1.46757739

D10 178.47957608

D11 -0.13718025

D12 179.20013107

D13 -179.55047527

D14 1.04106772

D15 0.22546892

D16 -0.92801144

D17 -178.99930951

D18 1.59508794

D19 0.22597188

D20 -178.60393514

D21 178.32579547

D22 -178.96874288

D23 -179.21090112

D24 179.68173163

D25 178.29206239

D26 178.54867180

D27 -179.21379951

D28 178.04835138

D29 179.05574121

1 2 1.5 3 2.0 4 1.5

2 5 1.5 6 2.0

3

4 5 1.5 10 2.0

5 7 2.0

6 8 1.5 9 1.5

7

8 14 1.0 15 1.5

9 16 1.5 17 1.0

10 11 1.5 12 1.5

11 20 1.5 21 1.0

12 13 1.5 19 1.0

13 22 1.5 23 1.0

14 24 1.0

15 18 1.5 25 1.0

16 18 1.5 26 1.0

17 27 1.0

18 28 1.0

19 29 1.0

20 22 1.5 30 1.0

21 31 1.0

22 32 1.0

23

24

25

26

27

28

29

30

31

32

Thank you for your letter

In fact my graduated Ph.D student left the. University, for that reason I cant help you

thank for your answer

but the total charge is zero, O=C doing double bond. Is it possible to make a single bond?

Dear Emine,

You do not have to worry if the carbonyl assigned as C=O or C-O since Gaussian 09 will recognize the right bonding between the carbon and oxygen. However you should type in the fourth line:

0     1

Zero for charge and 1 for multiplicity.

Rafik

Mrs/Miss Sas,

As Mr. Karaman has properly pointed out there is a single bond. The shown structures are visualized by GaussView, but by computation Gaussian should recognize C=O and C-O