(sec:nbo.detailed)= # Natural Bond Orbital (NBO) Analysis A popular and useful method for population analysis is the natural bond orbital analysis due to Weinhold and co-workers. It is implemented in the **NBO** program which is distributed in older versions via the CCL list and in newer versions via the University of Wisconsin/Madison. Information about the NBO program can be found at . In order to use it together with ORCA you need a version of the stand-alone executable. Starting with version 3.1.x ORCA can only be used with NBO6 or NBO7. To specify the NBO executable the environment variable NBOEXE=/full/name/of/nbo7-executable has to be set. As the NBO part of the interface is not independent of the integer data-type width (i4 or i8), the NBO executable which will be used together with ORCA has to be compiled using i4! ORCA features two methods to interface with the **NBO** program: `! NBO` keyword and the `%nbo`-block. The following example illustrates the use for formaldehyde: ```{literalinclude} ../../orca_working_input/C06S25_515.inp :language: orca ``` This produces the following output: ``` Now starting NBO.... *********************************** NBO 7.0 *********************************** N A T U R A L A T O M I C O R B I T A L A N D N A T U R A L B O N D O R B I T A L A N A L Y S I S ************************ development version (D000000) ************************ (c) Copyright 1996-2018 Board of Regents of the University of Wisconsin System on behalf of the Theoretical Chemistry Institute. All rights reserved. Cite this program [NBO 7.0.0 (15-Nov-2018)] as: NBO 7.0. E. D. Glendening, J. K. Badenhoop, A. E. Reed, J. E. Carpenter, J. A. Bohmann, C. M. Morales, P. Karafiloglou, C. R. Landis, and F. Weinhold, Theoretical Chemistry Institute, University of Wisconsin, Madison, WI (2018) /NPA / : Natural Population Analysis /NBO / : Natural Bond Orbital Analysis /AONBO / : Checkpoint the AO to NBO transformation /ARCHIVE/ : Write the archive file to lfn47 Job title: ORCA Job: NBO_1 NATURAL POPULATIONS: Natural atomic orbital occupancies NAO Atom No lang Type(AO) Occupancy Energy ------------------------------------------------------- 1 C 1 s Cor( 1s) 1.99997 -11.34329 2 C 1 s Val( 2s) 1.01533 -0.17540 3 C 1 s Ryd( 3s) 0.00701 0.61376 4 C 1 px Val( 2p) 0.81697 0.08822 5 C 1 px Ryd( 3p) 0.01268 0.63900 6 C 1 py Val( 2p) 1.09795 -0.01243 7 C 1 py Ryd( 3p) 0.00055 0.80803 8 C 1 pz Val( 2p) 0.66003 -0.03464 9 C 1 pz Ryd( 3p) 0.00283 0.62824 10 C 1 dxy Ryd( 3d) 0.00576 2.75039 11 C 1 dxz Ryd( 3d) 0.00375 2.25746 12 C 1 dyz Ryd( 3d) 0.00000 2.08566 13 C 1 dx2y2 Ryd( 3d) 0.00337 2.74845 14 C 1 dz2 Ryd( 3d) 0.00114 2.40647 15 O 2 s Cor( 1s) 1.99998 -20.56485 16 O 2 s Val( 2s) 1.70725 -0.92198 17 O 2 s Ryd( 3s) 0.00171 1.55322 18 O 2 px Val( 2p) 1.62177 -0.42255 19 O 2 px Ryd( 3p) 0.00079 1.29654 20 O 2 py Val( 2p) 1.91529 -0.46844 21 O 2 py Ryd( 3p) 0.00383 1.41052 22 O 2 pz Val( 2p) 1.32984 -0.28626 23 O 2 pz Ryd( 3p) 0.00011 1.30080 24 O 2 dxy Ryd( 3d) 0.00213 3.26414 25 O 2 dxz Ryd( 3d) 0.00340 3.20490 26 O 2 dyz Ryd( 3d) 0.00000 2.98918 27 O 2 dx2y2 Ryd( 3d) 0.00406 3.55008 28 O 2 dz2 Ryd( 3d) 0.00119 3.17511 29 H 3 s Val( 1s) 0.88576 0.07107 30 H 3 s Ryd( 2s) 0.00298 0.41181 31 H 3 px Ryd( 2p) 0.00030 2.18260 32 H 3 py Ryd( 2p) 0.00159 2.49146 33 H 3 pz Ryd( 2p) 0.00002 1.85643 34 H 4 s Val( 1s) 0.88576 0.07107 35 H 4 s Ryd( 2s) 0.00298 0.41181 36 H 4 px Ryd( 2p) 0.00030 2.18260 37 H 4 py Ryd( 2p) 0.00159 2.49146 38 H 4 pz Ryd( 2p) 0.00002 1.85643 Summary of Natural Population Analysis: Natural Population Natural --------------------------------------------- Atom No Charge Core Valence Rydberg Total -------------------------------------------------------------------- C 1 0.37265 1.99997 3.59028 0.03709 5.62735 O 2 -0.59134 1.99998 6.57415 0.01720 8.59134 H 3 0.10934 0.00000 0.88576 0.00489 0.89066 H 4 0.10934 0.00000 0.88576 0.00489 0.89066 ==================================================================== * Total * -0.00000 3.99995 11.93596 0.06408 16.00000 Natural Population --------------------------------------------------------- Core 3.99995 ( 99.9988% of 4) Valence 11.93596 ( 99.4664% of 12) Natural Minimal Basis 15.93592 ( 99.5995% of 16) Natural Rydberg Basis 0.06408 ( 0.4005% of 16) --------------------------------------------------------- Atom No Natural Electron Configuration ---------------------------------------------------------------------------- C 1 [core]2s( 1.02)2p( 2.57)3s( 0.01)3p( 0.02)3d( 0.01) O 2 [core]2s( 1.71)2p( 4.87)3d( 0.01) H 3 1s( 0.89) H 4 1s( 0.89) NATURAL BOND ORBITAL ANALYSIS: Occupancies Lewis Structure Low High Max Occ ------------------- ----------------- occ occ Cycle Ctr Thresh Lewis non-Lewis CR BD nC LP (L) (NL) ============================================================================ 1 2 1.90 15.89671 0.10329 2 4 0 2 0 0 ---------------------------------------------------------------------------- Structure accepted: No low occupancy Lewis orbitals ------------------------------------------------------- Core 3.99995 ( 99.999% of 4) Valence Lewis 11.89676 ( 99.140% of 12) ================== ============================= Total Lewis 15.89671 ( 99.354% of 16) ----------------------------------------------------- Valence non-Lewis 0.07835 ( 0.490% of 16) Rydberg non-Lewis 0.02493 ( 0.156% of 16) ================== ============================= Total non-Lewis 0.10329 ( 0.646% of 16) ------------------------------------------------------- (Occupancy) Bond orbital / Coefficients / Hybrids ------------------ Lewis ------------------------------------------------------ 1. (1.99997) CR ( 1) C 1 s(100.00%) 1.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 2. (1.99998) CR ( 1) O 2 s(100.00%) 1.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 3. (1.98853) LP ( 1) O 2 s( 56.22%)p 0.78( 43.73%)d 0.00( 0.05%) 0.0000 0.7496 -0.0170 0.6612 0.0069 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 -0.0201 0.0100 4. (1.91757) LP ( 2) O 2 s( 0.00%)p 1.00( 99.89%)d 0.00( 0.11%) 0.0000 0.0000 0.0000 -0.0000 -0.0000 0.9994 -0.0098 0.0000 -0.0000 -0.0330 -0.0000 0.0000 0.0000 -0.0000 5. (1.99996) BD ( 1) C 1- O 2 ( 33.33%) 0.5773* C 1 s( 0.00%)p 1.00( 99.44%)d 0.01( 0.56%) 0.0000 -0.0000 -0.0000 0.0000 -0.0000 -0.0000 0.0000 0.9951 -0.0652 -0.0000 0.0750 0.0000 -0.0000 0.0000 ( 66.67%) 0.8165* O 2 s( 0.00%)p 1.00( 99.75%)d 0.00( 0.25%) 0.0000 -0.0000 0.0000 0.0000 -0.0000 -0.0000 0.0000 0.9987 -0.0090 0.0000 -0.0505 0.0000 0.0000 -0.0000 6. (1.99975) BD ( 2) C 1- O 2 ( 32.59%) 0.5709* C 1 s( 32.18%)p 2.09( 67.35%)d 0.01( 0.46%) 0.0000 0.5628 0.0714 0.8149 0.0973 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 -0.0000 0.0000 0.0618 -0.0286 ( 67.41%) 0.8211* O 2 s( 43.84%)p 1.27( 55.85%)d 0.01( 0.31%) 0.0000 0.6615 0.0284 -0.7470 -0.0215 -0.0000 0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0000 0.0490 -0.0270 7. (1.99548) BD ( 1) C 1- H 3 ( 56.63%) 0.7526* C 1 s( 33.98%)p 1.94( 65.86%)d 0.00( 0.16%) 0.0000 0.5826 -0.0192 -0.3995 -0.0029 0.7063 -0.0087 0.0000 -0.0000 -0.0318 -0.0000 0.0000 -0.0180 -0.0153 ( 43.37%) 0.6585* H 3 s( 99.79%)p 0.00( 0.21%) 0.9989 -0.0095 0.0184 -0.0416 0.0000 8. (1.99548) BD ( 1) C 1- H 4 ( 56.63%) 0.7526* C 1 s( 33.98%)p 1.94( 65.86%)d 0.00( 0.16%) 0.0000 0.5826 -0.0192 -0.3995 -0.0029 -0.7063 0.0087 -0.0000 0.0000 0.0318 0.0000 0.0000 -0.0180 -0.0153 ( 43.37%) 0.6585* H 4 s( 99.79%)p 0.00( 0.21%) 0.9989 -0.0095 0.0184 0.0416 -0.0000 ---------------- non-Lewis ---------------------------------------------------- 9. (0.00000) BD*( 1) C 1- O 2 ( 66.67%) 0.8165* C 1 s( 0.00%)p 1.00( 99.44%)d 0.01( 0.56%) ( 33.33%) -0.5773* O 2 s( 0.00%)p 1.00( 99.75%)d 0.00( 0.25%) 10. (0.00000) BD*( 2) C 1- O 2 ( 67.41%) 0.8211* C 1 s( 32.18%)p 2.09( 67.35%)d 0.01( 0.46%) ( 32.59%) -0.5709* O 2 s( 43.84%)p 1.27( 55.85%)d 0.01( 0.31%) 11. (0.03918) BD*( 1) C 1- H 3 ( 43.37%) 0.6585* C 1 s( 33.98%)p 1.94( 65.86%)d 0.00( 0.16%) 0.0000 -0.5826 0.0192 0.3995 0.0029 -0.7063 0.0087 -0.0000 0.0000 0.0318 0.0000 0.0000 0.0180 0.0153 ( 56.63%) -0.7526* H 3 s( 99.79%)p 0.00( 0.21%) -0.9989 0.0095 -0.0184 0.0416 -0.0000 12. (0.03918) BD*( 1) C 1- H 4 ( 43.37%) 0.6585* C 1 s( 33.98%)p 1.94( 65.86%)d 0.00( 0.16%) 0.0000 -0.5826 0.0192 0.3995 0.0029 0.7063 -0.0087 0.0000 -0.0000 -0.0318 -0.0000 0.0000 0.0180 0.0153 ( 56.63%) -0.7526* H 4 s( 99.79%)p 0.00( 0.21%) -0.9989 0.0095 -0.0184 -0.0416 0.0000 13. (0.00969) RY ( 1) C 1 s( 29.83%)p 2.30( 68.57%)d 0.05( 1.60%) 0.0000 -0.0565 0.5432 -0.1169 0.8198 0.0000 -0.0000 0.0000 -0.0000 -0.0000 0.0000 0.0000 0.1087 -0.0648 14. (0.00517) RY ( 2) C 1 s( 0.00%)p 1.00( 9.56%)d 9.46( 90.44%) 0.0000 0.0000 -0.0000 0.0000 -0.0000 0.0465 0.3057 0.0000 -0.0000 0.9510 0.0000 0.0000 -0.0000 -0.0000 15. (0.00001) RY ( 3) C 1 s( 20.02%)p 0.82( 16.47%)d 3.17( 63.52%) 16. (0.00000) RY ( 4) C 1 s( 0.00%)p 1.00( 90.64%)d 0.10( 9.36%) 17. (0.00000) RY ( 5) C 1 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%) 18. (0.00000) RY ( 6) C 1 s( 42.72%)p 0.35( 15.02%)d 0.99( 42.26%) 19. (0.00000) RY ( 7) C 1 s( 0.00%)p 1.00( 0.56%)d99.99( 99.44%) 20. (0.00000) RY ( 8) C 1 s( 0.00%)p 0.00( 0.00%)d 1.00(100.00%) 21. (0.00000) RY ( 9) C 1 s( 7.29%)p 0.09( 0.66%)d12.63( 92.05%) 22. (0.00368) RY ( 1) O 2 s( 0.00%)p 1.00( 98.96%)d 0.01( 1.04%) 0.0000 -0.0000 -0.0000 0.0000 0.0000 0.0064 0.9948 -0.0000 0.0000 -0.1018 0.0000 0.0000 -0.0000 0.0000 23. (0.00014) RY ( 2) O 2 s( 35.10%)p 1.44( 50.60%)d 0.41( 14.30%) 0.0000 -0.0178 0.5922 0.0556 -0.7091 0.0000 -0.0000 -0.0000 0.0000 -0.0000 0.0000 0.0000 0.3336 -0.1780 24. (0.00000) RY ( 3) O 2 s( 56.05%)p 0.25( 13.79%)d 0.54( 30.17%) 25. (0.00000) RY ( 4) O 2 s( 0.00%)p 1.00(100.00%)d 0.00( 0.00%) 26. (0.00000) RY ( 5) O 2 s( 0.00%)p 1.00( 1.14%)d86.35( 98.86%) 27. (0.00000) RY ( 6) O 2 s( 0.00%)p 1.00( 0.25%)d99.99( 99.75%) 28. (0.00000) RY ( 7) O 2 s( 0.00%)p 0.00( 0.00%)d 1.00(100.00%) 29. (0.00000) RY ( 8) O 2 s( 6.72%)p 5.27( 35.42%)d 8.61( 57.85%) 30. (0.00000) RY ( 9) O 2 s( 2.07%)p 0.30( 0.61%)d47.00( 97.32%) 31. (0.00308) RY ( 1) H 3 s( 99.42%)p 0.01( 0.58%) 0.0096 0.9970 -0.0710 -0.0281 0.0000 32. (0.00002) RY ( 2) H 3 s( 0.22%)p99.99( 99.78%) 33. (0.00002) RY ( 3) H 3 s( 0.00%)p 1.00(100.00%) 34. (0.00001) RY ( 4) H 3 s( 0.57%)p99.99( 99.43%) 35. (0.00308) RY ( 1) H 4 s( 99.42%)p 0.01( 0.58%) 0.0096 0.9970 -0.0710 0.0281 0.0000 36. (0.00002) RY ( 2) H 4 s( 0.22%)p99.99( 99.78%) 37. (0.00002) RY ( 3) H 4 s( 0.00%)p 1.00(100.00%) 38. (0.00001) RY ( 4) H 4 s( 0.57%)p99.99( 99.43%) NHO DIRECTIONALITY AND BOND BENDING (deviation from line of nuclear centers at the position of maximum hybrid amplitude) [Thresholds for printing: angular deviation > 1.0 degree] p- or d-character > 25.0% orbital occupancy > 0.10e Line of Centers Hybrid 1 Hybrid 2 --------------- ------------------- ------------------ NBO Theta Phi Theta Phi Dev Theta Phi Dev =============================================================================== 3. LP ( 1) O 2 -- -- 90.0 0.0 -- -- -- -- 4. LP ( 2) O 2 -- -- 90.0 90.7 -- -- -- -- 5. BD ( 1) C 1- O 2 90.0 0.0 3.0 0.0 87.0 178.7 180.0 88.7 SECOND ORDER PERTURBATION THEORY ANALYSIS OF FOCK MATRIX IN NBO BASIS Threshold for printing: 0.50 kcal/mol E(2) E(NL)-E(L) F(L,NL) Donor (L) NBO Acceptor (NL) NBO kcal/mol a.u. a.u. =============================================================================== within unit 1 3. LP ( 1) O 2 13. RY ( 1) C 1 8.58 1.40 0.098 4. LP ( 2) O 2 11. BD*( 1) C 1- H 3 26.11 1.16 0.156 4. LP ( 2) O 2 12. BD*( 1) C 1- H 4 26.11 1.16 0.156 4. LP ( 2) O 2 14. RY ( 2) C 1 5.72 3.06 0.118 4. LP ( 2) O 2 26. RY ( 5) O 2 0.73 3.75 0.047 7. BD ( 1) C 1- H 3 12. BD*( 1) C 1- H 4 0.74 1.42 0.029 7. BD ( 1) C 1- H 3 22. RY ( 1) O 2 2.25 2.12 0.062 8. BD ( 1) C 1- H 4 11. BD*( 1) C 1- H 3 0.74 1.42 0.029 8. BD ( 1) C 1- H 4 22. RY ( 1) O 2 2.25 2.12 0.062 NATURAL BOND ORBITALS (Summary): Principal Delocalizations NBO Occupancy Energy (geminal,vicinal,remote) =============================================================================== Molecular unit 1 (CH2O) ------ Lewis -------------------------------------- 1. CR ( 1) C 1 1.99997 -11.34329 2. CR ( 1) O 2 1.99998 -20.56485 3. LP ( 1) O 2 1.98853 -0.81352 13(v) 4. LP ( 2) O 2 1.91757 -0.46975 11(v),12(v),14(v),26(g) 5. BD ( 1) C 1- O 2 1.99996 -0.53505 6. BD ( 2) C 1- O 2 1.99975 -1.23345 7. BD ( 1) C 1- H 3 1.99548 -0.72703 22(v),12(g) 8. BD ( 1) C 1- H 4 1.99548 -0.72703 22(v),11(g) ------ non-Lewis ---------------------------------- 9. BD*( 1) C 1- O 2 0.00000 0.20704 10. BD*( 2) C 1- O 2 0.00000 0.95146 11. BD*( 1) C 1- H 3 0.03918 0.69317 12. BD*( 1) C 1- H 4 0.03918 0.69317 13. RY ( 1) C 1 0.00969 0.58169 14. RY ( 2) C 1 0.00517 2.58837 15. RY ( 3) C 1 0.00001 1.75652 16. RY ( 4) C 1 0.00000 0.96046 17. RY ( 5) C 1 0.00000 0.64510 18. RY ( 6) C 1 0.00000 1.49223 19. RY ( 7) C 1 0.00000 2.24615 20. RY ( 8) C 1 0.00000 2.08566 21. RY ( 9) C 1 0.00000 2.49414 22. RY ( 1) O 2 0.00368 1.39676 23. RY ( 2) O 2 0.00014 1.56107 24. RY ( 3) O 2 0.00000 2.18160 25. RY ( 4) O 2 0.00000 1.30222 26. RY ( 5) O 2 0.00000 3.27920 27. RY ( 6) O 2 0.00000 3.20505 28. RY ( 7) O 2 0.00000 2.98918 29. RY ( 8) O 2 0.00000 2.69359 30. RY ( 9) O 2 0.00000 3.12898 31. RY ( 1) H 3 0.00308 0.41874 32. RY ( 2) H 3 0.00002 2.57996 33. RY ( 3) H 3 0.00002 1.85643 34. RY ( 4) H 3 0.00001 2.06898 35. RY ( 1) H 4 0.00308 0.41874 36. RY ( 2) H 4 0.00002 2.57996 37. RY ( 3) H 4 0.00002 1.85643 38. RY ( 4) H 4 0.00001 2.06898 ------------------------------- Total Lewis 15.89671 ( 99.3545%) Valence non-Lewis 0.07835 ( 0.4897%) Rydberg non-Lewis 0.02493 ( 0.1558%) ------------------------------- Total unit 1 16.00000 (100.0000%) Charge unit 1 0.00000 $CHOOSE LONE 2 2 END BOND D 1 2 S 1 3 S 1 4 END $END NBO analysis completed in 0.05 CPU seconds (0 wall seconds) Maximum scratch memory used by NBO was 297106 words (2.27 MB) Stopping NBO...Storing NBOs: NBO_1.nbo *** returned from NBO program *** ``` Thus, in this example the NBO analysis of formaldehyde shows that a single Lewis structure is dominant with single bonds between C and H, a double bond between C and O and two lone pairs at the oxygen -- just as ordinary chemical arguments would imply. In addition, the program produces the four corresponding valence antibonds. The remaining components of the basis set span the "Rydberg" space and lead to semilocalized, orthogonal orbitals that are assigned to single atoms (Note the nomenclature: BD $=$ bond, BD\* $=$ antibond, LP $=$ lone pair, CR $=$ core orbital, RY$=$ Rydberg orbital). The NPA analysis shows a patially negative oxygen and partially positive carbon and hydrogen atoms. Additionally, the NBO orbitals are stored in the ORCA .gbw file format as `jobname.nbo`. This file can be used for further analysis and usage with ORCA e.g. for plotting orbitals via `orca_plot`. The **NBO** program has many additional features and analysis tools. The features that are implemented in ORCA can be controlled via the `%nbo`-block ```orca %nbo NBOKEYLIST = "$NBO ... $END" DELKEYLIST = "$DEL ... $END" COREKEYLIST = "$CORE ... $END" NRTSTRKEYLIST = "$NRTSTR ... $END" NPEPAKEYLIST = "$NPEPA ... $END" end ``` The syntax of the respective keylists is given by the NBO6.x/NBO7.x manual. Specifying the single `! NBO` keyword corresponds to the `%nbo`-block ```orca %nbo NBOKEYLIST = "$NBO NBO NPA AONBO=C ARCHIVE $END" end ``` The full set of features beyond those which can be give via the `%nbo` block can be accessed using the file `FILE.47`, which is generated by the NBO program. This is an ascii file that can be edited with a text editor. Add or remove keywords in the corresponding blocks as needed and call the gennbo program like ```orca gennbo < FILE.47 >jobname.nboout ``` (fig:732)= :::{subfigure} ABC|DEF :subcaptions: below :class-grid: outline ![(a) π](../../images/732.*) ![(b) π - LP](../../images/733.*) ![(c) π*](../../images/734.*) ![(d) σ](../../images/735.*) ![(e) σ - LP](../../images/736.*) ![(f) σ*](../../images/737.*) Six NBOs of the H$_2$CO molecule. Shown are the occupied bonding $\pi$ and $\sigma$ orbitals (left) for C and O, the two oxygen lone pairs (middle) and the two $\pi^*$ and $\sigma^*$ antibonding orbitals (right). ::: The `FILE.47` file looks like: ```orca $GENNBO NATOMS=4 NBAS=38 UPPER BODM FORMAT $END $NBO $END $COORD ORCA Job: check 6 6 0.000000 0.000000 0.000000 8 8 2.267671 0.000000 0.000000 1 1 -1.039349 1.800206 0.000000 1 1 -1.039349 -1.800206 0.000000 $END $BASIS ``` If you have no need for this (rather large) file, then you have to delete it manually! (sec:nbo.deletions.detailed)= ## NBO Deletions An advanced feature, which has been implemented via the ORCA-NBO interface, is the possibility of using deletions. ```{literalinclude} ../../orca_working_input/C06S26_520.inp :language: orca ``` The `DELKEYLIST` provides NBO with the task to perform certain deletions of orbitals/interactions. Per deletion ORCA calculates a new Fock matrix on basis of an NBO density corresponding to the deletions: ``` Stopping NBO...Starting NBO again for $del instructions... LEWIS: Delete all non-Lewis NBOs Deletion of the following orbitals from the NBO Fock matrix: 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 Orbital occupancies: Orbital No deletions This deletion Change ------------------------------------------------------------------------------ 1. CR ( 1) C 1 1.99978 2.00000 0.00022 2. CR ( 1) N 2 1.99983 2.00000 0.00017 3. LP ( 1) N 2 1.97796 2.00000 0.02204 4. BD ( 1) C 1- N 2 1.99846 2.00000 0.00154 5. BD ( 1) C 1- H 3 1.99858 2.00000 0.00142 6. BD ( 1) C 1- H 4 1.99406 2.00000 0.00594 7. BD ( 1) C 1- H 5 1.99406 2.00000 0.00594 8. BD ( 1) N 2- H 6 1.99440 2.00000 0.00560 9. BD ( 1) N 2- H 7 1.99440 2.00000 0.00560 10. BD*( 1) C 1- N 2 0.00009 0.00000 -0.00009 11. BD*( 1) C 1- H 3 0.01567 0.00000 -0.01567 12. BD*( 1) C 1- H 4 0.00763 0.00000 -0.00763 13. BD*( 1) C 1- H 5 0.00763 0.00000 -0.00763 14. BD*( 1) N 2- H 6 0.00424 0.00000 -0.00424 15. BD*( 1) N 2- H 7 0.00424 0.00000 -0.00424 16. RY ( 1) C 1 0.00094 0.00000 -0.00094 17. RY ( 2) C 1 0.00034 0.00000 -0.00034 18. RY ( 3) C 1 0.00020 0.00000 -0.00020 19. RY ( 4) C 1 0.00001 0.00000 -0.00001 20. RY ( 1) N 2 0.00114 0.00000 -0.00114 21. RY ( 2) N 2 0.00044 0.00000 -0.00044 22. RY ( 3) N 2 0.00034 0.00000 -0.00034 23. RY ( 4) N 2 0.00001 0.00000 -0.00001 24. RY ( 1) H 3 0.00163 0.00000 -0.00163 25. RY ( 1) H 4 0.00079 0.00000 -0.00079 26. RY ( 1) H 5 0.00079 0.00000 -0.00079 27. RY ( 1) H 6 0.00117 0.00000 -0.00117 28. RY ( 1) H 7 0.00117 0.00000 -0.00117 NEXT STEP: Perform one SCF cycle to evaluate the energy of the new density matrix constructed from the deleted NBO Fock matrix. ------------------------------------------------------------------------------ Copying NBO density... Calculating new Fock-Matrix... Calculating Fock-Matrix...done! New NBO energy via Fock-Matrix: -94.629937 Starting NBO again for $del/return energy instructions... ------------------------------------------------------------------------------ Energy of deletion : -94.629936711 Total SCF energy : -94.679444929 ------------------- Energy change : 0.049508 a.u., 31.067 kcal/mol ------------------------------------------------------------------------------ ``` Multiple deletions can also be specified, as can be seen for this example. The output then also contains the additional energy values: ``` Starting NBO again for $del instructions... Deletion of the following NBO Fock matrix elements: 3, 11; Orbital occupancies: Orbital No deletions This deletion Change ------------------------------------------------------------------------------ 1. CR ( 1) C 1 1.99978 1.99978 -0.00000 2. CR ( 1) N 2 1.99983 1.99983 -0.00000 3. LP ( 1) N 2 1.97796 1.99348 0.01552 4. BD ( 1) C 1- N 2 1.99846 1.99860 0.00015 5. BD ( 1) C 1- H 3 1.99858 1.99845 -0.00014 6. BD ( 1) C 1- H 4 1.99406 1.99404 -0.00002 7. BD ( 1) C 1- H 5 1.99406 1.99404 -0.00002 8. BD ( 1) N 2- H 6 1.99440 1.99450 0.00011 9. BD ( 1) N 2- H 7 1.99440 1.99450 0.00011 10. BD*( 1) C 1- N 2 0.00009 0.00008 -0.00000 11. BD*( 1) C 1- H 3 0.01567 0.00042 -0.01525 12. BD*( 1) C 1- H 4 0.00763 0.00780 0.00017 13. BD*( 1) C 1- H 5 0.00763 0.00780 0.00017 14. BD*( 1) N 2- H 6 0.00424 0.00424 0.00000 15. BD*( 1) N 2- H 7 0.00424 0.00424 0.00000 16. RY ( 1) C 1 0.00094 0.00063 -0.00031 17. RY ( 2) C 1 0.00034 0.00034 0.00000 18. RY ( 3) C 1 0.00020 0.00032 0.00012 19. RY ( 4) C 1 0.00001 0.00002 0.00001 20. RY ( 1) N 2 0.00114 0.00115 0.00001 21. RY ( 2) N 2 0.00044 0.00044 0.00000 22. RY ( 3) N 2 0.00034 0.00034 0.00000 23. RY ( 4) N 2 0.00001 0.00001 0.00000 24. RY ( 1) H 3 0.00163 0.00092 -0.00072 25. RY ( 1) H 4 0.00079 0.00083 0.00005 26. RY ( 1) H 5 0.00079 0.00083 0.00005 27. RY ( 1) H 6 0.00117 0.00118 0.00000 28. RY ( 1) H 7 0.00117 0.00118 0.00000 NEXT STEP: Perform one SCF cycle to evaluate the energy of the new density matrix constructed from the deleted NBO Fock matrix. ------------------------------------------------------------------------------ Copying NBO density... Calculating new Fock-Matrix... Calculating Fock-Matrix...done! New NBO energy via Fock-Matrix: -94.668383 Starting NBO again for $del/return energy instructions... ------------------------------------------------------------------------------ Energy of deletion : -94.668383268 Total SCF energy : -94.679444929 ------------------- Energy change : 0.011062 a.u., 6.941 kcal/mol ------------------------------------------------------------------------------ ``` ::: center *NOTE: Deletions are only implemented for SCF methods!* ::: (sec:nbo.posthfdensities.detailed)= ## NBO for Post-HF Densities NBO analysis can be performed on all methods producing a density. In some methods the density generation has to be specified explictly, e. g. for MP2 calculations this would be: ```{literalinclude} ../../orca_working_input/C06S26_521.inp :language: orca ``` The output will contain both the NBO analysis of the SCF density as well as of the MP2 relaxed density. An NBO analysis of a density generated by the MDCI module can be specified as follows: ```{literalinclude} ../../orca_working_input/C06S26_522.inp :language: orca ``` Again, the output will contain both the NBO analysis of the SCF density as well es of the CISD linearized density. (sec:nbo.ncsanalysis.detailed)= ## Natural Chemical Shielding Analysis (NCS) For closed-shell calculations of NMR chemical shielding at the SCF level (see sections {ref}`sec:properties.nmr.shift.typical` and {ref}`sec:properties.eprnmr.detailed`), the NCS analysis can be requested by adding `NCS` to the `NBOKEYLIST`. The `NCS` keyword accepts the arguments `U`, `I`, `CSA`, `XYZ`, and `MO` to analyze the "unperturbed", "induced", anisotropic, Cartesian, and canonical MO contributions to the shielding tensors, respectively, as well as a decimal number for the printing threshold (in ppm). For more information, consult the NBO manual and the original publication.{cite}`Bohmann1997-NCS` ```{literalinclude} ../../orca_working_input/NCS_example.inp :language: orca ``` ``` Summary of isotropic NMR chemical shielding Total Lewis (L) and non-Lewis (NL) contributions: (ppm) NBO H 1 C 2 N 3 --------------- ------- ------- ------- 1. C 2(cr) L -0.18 200.26 0.18 NL -0.02 0.02 0.00 2. N 3(cr) L -0.03 -0.12 235.18 NL 0.00 0.01 0.02 3. N 3(lp) L 1.02 -33.00 -151.92 NL -1.04 1.81 12.18 4. H 1- C 2 L 25.75 -49.28 -20.30 NL -1.24 6.10 2.26 5. C 2- N 3 L 2.29 15.40 13.66 NL 0.02 0.00 -0.00 6. C 2- N 3 L 2.29 15.40 13.66 NL 0.02 0.00 -0.00 7. C 2- N 3 L 0.46 -77.94 -151.00 NL 0.05 -4.41 0.95 --------------- ------- ------- ------- Lewis 31.59 70.70 -60.53 non-Lewis -2.21 3.53 15.42 --------------- ------- ------- ------- Total 29.38 74.23 -45.11 ```