.. _ptb: ------- PTB ------- Introducing PTB ======================== ``PTB`` stands for density (**P**) tight-binding (**TB**), a method that emulates the density matrix of a :math:`{\omega}`\ B97X-3c range-separated hybrid DFT calculation (see also below). .. figure:: ../figures/ptb_cover_image.png :align: center PTB can be used out-of-the-box to various electronic structure properties for molecules composed of all spd-block elements up to *Z=86*. The key improvement is the substitution of commonly used minimal atomic orbital basis sets with an extended and properly polarized basis set (vDZP). Its main purpose is to provide extremely fast the one-particle electronic density matrix **P** and derived properties, such as atomic charges, shell populations, dipole moments, and geometric derivatives as well as static dipole polarizabilities. For a wide range of molecules from various chemical compound classes (organic, inorganic, transition metal complexes, clusters, and aggregates), including multiple anions/cations, excellent agreement between PTB and :math:`{\omega}`\ B97X-3c computed properties is obtained. Typical RMSDs are 0.02 e\ :sup:`-` for atomic charges or shell populations, with deviations of approximately 5% to 10% for dipole moments and polarizabilities. Artificial charge transfer, such as in zwitterions, or SCF convergence issues in electronically challenging small-gap systems is largely avoided, which also results from the applied non-iterative, two-step diagonalization scheme. No energy expression is available currently, and the entire development was focused on reproducing the DFT density matrix and some of its response features as accurately as possible. PTB has been published in `The Journal of Chemical Physics `_: Grimme, S.; Müller, M.; Hansen, A. A Non-Self-Consistent Tight-Binding Electronic Structure Potential in a Polarized Double-ζ Basis Set for All *spd*-Block Elements up to *Z* = 86. *J. Chem. Phys.* 2023, **158** (12), 124111. DOI: `10.1063/5.0137838 `_ For further information on :math:`{\omega}`\ B97X-3c, see: `Müller, M.; Hansen, A.; Grimme, S. J. Chem. Phys. 2023, 158 (1), 014103 `_. Basic usage ============================ PTB is implemented in the ``xtb`` program. It extends the portfolio of the package by the non-self-consistent density tight-binding method PTB. It is invoked with the keyword ``--ptb`` as shown in the example below. .. tab-set:: .. tab-item:: CLI input .. code-block:: none > xtb coord.xyz --ptb --json .. tab-item:: coord.xyz .. figure:: ../figures/benzene_dimer.png :width: 75% :alt: A cofacial NCI complex of benzene and nitrobenzene for testing PTB. A cofacial NCI complex of benzene and nitrobenzene for testing PTB. .. code-block:: none 26 C -1.20618 0.69599 1.75211 C -1.20379 -0.70017 1.75215 C 0.00616 -1.39690 1.75210 C 1.21824 -0.70002 1.75171 C 1.23033 0.70989 1.75117 C 0.00125 1.40067 1.75172 H 2.14504 -1.25925 1.74975 H -0.02278 2.48280 1.74976 H -2.14520 1.23405 1.75041 H -2.14028 -1.24255 1.75044 H 0.00554 -2.47919 1.75040 C -1.21072 0.69984 -1.75114 C -1.21074 -0.69902 -1.75149 C 0.00072 -1.39843 -1.75114 C 1.21220 -0.69897 -1.75037 C 1.21222 0.69988 -1.74995 C 0.00077 1.39929 -1.75036 H 2.14941 -1.24008 -1.74839 H 2.14945 1.24099 -1.74755 H 0.00077 2.48148 -1.74837 H -2.14799 1.24091 -1.74971 H -2.14800 -1.24014 -1.75028 H 0.00066 -2.48066 -1.74972 N 2.46723 1.42685 1.74737 O 2.47280 2.62117 1.74468 O 3.50640 0.83800 1.74471 .. tab-item:: Standard output .. code-block:: none ------------------------------------------------- | P T B | ------------------------------------------------- Reference 10.1063/5.0137838 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,@@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,* @,,,,,,,,@///////////////#,,,,,,,,,@ @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@/////////////////,,,,,,,,( @,,,,,,,,@////////////////@,,,,,,,,@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,% @@@@@@@@@@@@@@@@@@ @@@@@@@@@@@@@@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,&////@,,,,,,,,,,,,,,,,,///@,,,,,,,,,,,,,,@ @,,,,,,,,,,,,,,,,,,,,,,,,,,,,,@///////@,,,,,,,,,,,,,,,,,,//@,,,,,,,,,,,,,,,,@ @,,,,,,,,@///////////////////////////////////@,,,#/////////@,,,@////////*,,,@ @,,,,,,,,@/////////@ ////////////////////////@,,,#/////////@,,,@////////*,,,@ @,,,,,,,,@///// %@@ ( @@@ (@ @@@ @//////////@,,,#/////////@,,,@////////*,,,@ @,,,,,,,,@////( @//@ ( @@@ @@ @//.@//////////@,,,#/////////@,,,,,,,,,,,,,,,* @,,,,,,,,@///// @//@ ( @////@ @//.@//////////@,,,#/////////@,,,,,,,,,,,,,,,,@ @,,,,,,,,@//////@@@@@/(@@@@/@@@//@@//////////@,,,#/////////@,,,@////////(,,,,@ @,,,,,,,,@///////////#@@/ @//////////////////@,,,#/////////@,,,@/////////,,,,@ @,,,,,,,,@//// .@@/(/# @@ @@/@ /// @/////////@,,,#/////////@,,,@/////////,,,,@ @,,,,,,,,@////% @/# @/ @//@ /// @/////////@,,,#/////////@,,,@////////@,,,,@ @,,,,,,,,@////////@ /# @/ @//@ /// @/////////@,,,#/////////@,,,,,,,,,,,,,,,,@ &@@@@@@@@@/////@@@@//(@@/#@@(/#@@@ @ @@@ @ ................................................... : SETUP : :.................................................: : # atomic orbitals 250 : : # shells 108 : : # electrons 76 : : # open shells 0 : : max. iterations 2 : : Hamiltonian PTB : : PC potential false : : electronic temp. 300.0000000 K : : -> integral cutoff 0.2500000E+02 : : verbosity level 2 : ................................................... --- Calculation progress: --- 1st iteration... 2nd iteration... --- Two-step SCF done. --- ------------------------------------------------- | Property Printout | ------------------------------------------------- * Orbital Energies and Occupations # Occupation Energy/Eh Energy/eV ------------------------------------------------------------- 1 2.0000 -1.4335353 -39.0085 ... ... ... ... 26 2.0000 -0.5045711 -13.7301 27 2.0000 -0.5040396 -13.7156 28 2.0000 -0.4808924 -13.0857 29 2.0000 -0.4722708 -12.8511 30 2.0000 -0.4561747 -12.4131 31 2.0000 -0.4557899 -12.4027 32 2.0000 -0.4309614 -11.7271 33 2.0000 -0.4259563 -11.5909 34 2.0000 -0.4044794 -11.0064 35 2.0000 -0.3964229 -10.7872 36 2.0000 -0.3947316 -10.7412 37 2.0000 -0.3670100 -9.9869 38 2.0000 -0.3665408 -9.9741 (HOMO) 39 -0.0239028 -0.6504 (LUMO) 40 0.0361502 0.9837 41 0.0638157 1.7365 42 0.0661394 1.7997 43 0.1022883 2.7834 44 0.1226305 3.3369 45 0.1550123 4.2181 46 0.2012073 5.4751 47 0.2105286 5.7288 48 0.2372001 6.4545 49 0.2389287 6.5016 ... ... ... 250 1880.0926856 51159.9260 ------------------------------------------------------------- HL-Gap 0.3426379 Eh 9.3237 eV Fermi-level 0.0000000 Eh 0.0000 eV * Atomic partial charges (q) Shell populations (p) ------------------------------------------------------------------------------------ # sym q 1 2 3 4 5 ------------------------------------------------------------------------------------ 1 C -0.02580 0.56624 0.25826 2.14868 0.77647 0.27615 2 C -0.01955 0.56946 0.25888 2.13958 0.76848 0.28315 3 C -0.02579 0.56627 0.25829 2.14863 0.77652 0.27608 4 C -0.00674 0.57136 0.26101 2.13410 0.76488 0.27539 5 C -0.01140 0.56315 0.24359 2.13512 0.71189 0.35765 6 C -0.00687 0.57136 0.26099 2.13427 0.76482 0.27544 7 H 0.05450 0.66023 0.14231 0.14297 8 H 0.05446 0.66025 0.14231 0.14298 9 H 0.05064 0.66417 0.14119 0.14400 10 H 0.04931 0.66558 0.14146 0.14366 11 H 0.05064 0.66417 0.14120 0.14399 12 C -0.04504 0.56668 0.25975 2.14638 0.78730 0.28493 13 C -0.04650 0.56670 0.25972 2.14711 0.78765 0.28531 14 C -0.04508 0.56668 0.25975 2.14641 0.78730 0.28493 15 C -0.03969 0.56642 0.25979 2.14367 0.78616 0.28365 16 C -0.03467 0.56633 0.25982 2.14085 0.78496 0.28271 17 C -0.03968 0.56643 0.25979 2.14367 0.78616 0.28363 18 H 0.04302 0.66835 0.14362 0.14502 19 H 0.04581 0.66728 0.14289 0.14402 20 H 0.04301 0.66836 0.14361 0.14502 21 H 0.04078 0.66938 0.14399 0.14585 22 H 0.04037 0.66955 0.14405 0.14602 23 H 0.04076 0.66940 0.14399 0.14585 24 N 0.09115 0.72096 0.24406 2.47323 0.78151 0.68909 25 O -0.12891 1.16607 0.40893 3.39118 1.05904 0.10369 26 O -0.12874 1.16608 0.40896 3.39091 1.05912 0.10367 ------------------------------------------------------------------------------------ total: 0.00000 Wiberg/Mayer (AO) data. largest (>0.10) Wiberg bond orders for each atom --------------------------------------------------------------------------- # Z sym total # sym WBO # sym WBO # sym WBO --------------------------------------------------------------------------- 1 6 C 3.965 -- 6 C 1.445 2 C 1.429 9 H 0.989 2 6 C 3.977 -- 1 C 1.429 3 C 1.429 10 H 0.993 3 6 C 3.965 -- 4 C 1.445 2 C 1.429 11 H 0.989 4 6 C 3.967 -- 3 C 1.445 5 C 1.403 7 H 0.982 5 6 C 4.006 -- 4 C 1.403 6 C 1.403 24 N 1.052 6 6 C 3.967 -- 1 C 1.445 5 C 1.403 8 H 0.982 7 1 H 1.016 -- 4 C 0.982 8 1 H 1.016 -- 6 C 0.982 9 1 H 1.035 -- 1 C 0.989 10 1 H 1.038 -- 2 C 0.993 11 1 H 1.035 -- 3 C 0.989 12 6 C 3.992 -- 13 C 1.441 17 C 1.440 21 H 0.993 13 6 C 3.994 -- 12 C 1.441 14 C 1.441 22 H 0.994 14 6 C 3.992 -- 13 C 1.441 15 C 1.440 23 H 0.993 15 6 C 3.987 -- 14 C 1.440 16 C 1.439 18 H 0.991 16 6 C 3.980 -- 15 C 1.439 17 C 1.439 19 H 0.988 17 6 C 3.987 -- 12 C 1.440 16 C 1.439 20 H 0.991 18 1 H 1.038 -- 15 C 0.991 19 1 H 1.033 -- 16 C 0.988 20 1 H 1.038 -- 17 C 0.991 21 1 H 1.041 -- 12 C 0.993 22 1 H 1.042 -- 13 C 0.994 23 1 H 1.041 -- 14 C 0.993 24 7 N 4.311 -- 26 O 1.621 25 O 1.621 5 C 1.052 25 8 O 1.880 -- 24 N 1.621 26 O 0.198 26 8 O 1.880 -- 24 N 1.621 25 O 0.198 --------------------------------------------------------------------------- Topologies differ in total number of bonds Writing topology from bond orders to xtbtopo.mol -------------------------------------- Molecular dipole moment (a.u.) X Y Z -------------------------------------- -1.6560 -0.9605 0.0032 -------------------------------------- Total dipole moment (a.u. / Debye): 1.9144 4.8658 -------------------------------------- Molecular quadrupole tensor: (a.u.) X Y Z X -4.6099 Y -18.7964 6.5225 Z -17.6585 -10.2393 -1.9126 .. tab-item:: JSON output .. code-block:: none { "total energy": 0.00000000, "HOMO-LUMO gap / eV": 9.32365300, "electronic energy": 0.00000000, "dipole / a.u.": [ -1.65595034, -0.96050070, 0.00324936], "partial charges": [ -0.02580418, -0.01955062, -0.02578955, -0.00673978, -0.01139657, -0.00687004, 0.05449601, 0.05446298, 0.05064076, 0.04930957, 0.05064248, -0.04504331, -0.04650347, -0.04507944, -0.03968609, -0.03467388, -0.03967838, 0.04301740, 0.04581142, 0.04301236, 0.04078359, 0.04037447, 0.04075952, 0.09114600, -0.12890616, -0.12873510], "shell charges": [ [ -0.00957618, -0.00706229, -0.04112235, -0.01900655, 0.05096319], [ -0.01279822, -0.00767786, -0.03201783, -0.01101893, 0.04396222], [ -0.00960229, -0.00708624, -0.04107428, -0.01905729, 0.05103056], [ -0.01469682, -0.00980551, -0.02654501, -0.00741039, 0.05171796], [ -0.00648151, 0.00761632, -0.02756281, 0.04557390, -0.03054247], [ -0.01469601, -0.00978240, -0.02671271, -0.00735074, 0.05167182], [ 0.03241257, -0.00070811, 0.02279154], [ 0.03239064, -0.00070551, 0.02277785], [ 0.02847477, 0.00040602, 0.02175998], [ 0.02706603, 0.00014321, 0.02210034], [ 0.02847696, 0.00040179, 0.02176373], [ -0.01001242, -0.00854798, -0.03882204, -0.02983659, 0.04217572], [ -0.01003868, -0.00851992, -0.03955334, -0.03018934, 0.04179781], [ -0.01001808, -0.00854912, -0.03885175, -0.02983662, 0.04217614], [ -0.00975838, -0.00858791, -0.03610517, -0.02869582, 0.04346118], [ -0.00966665, -0.00861631, -0.03329379, -0.02749367, 0.04439655], [ -0.00976372, -0.00858896, -0.03610916, -0.02869079, 0.04347425], [ 0.02429422, -0.00201553, 0.02073871], [ 0.02536325, -0.00128692, 0.02173510], [ 0.02428199, -0.00201121, 0.02074158], [ 0.02325873, -0.00238696, 0.01991182], [ 0.02308916, -0.00245145, 0.01973676], [ 0.02324259, -0.00239520, 0.01991213], [ 0.07527729, 0.07343734, 0.26312472, 0.19945280, -0.52014616], [ -0.08146427, -0.02758942, -0.06355142, 0.07033950, -0.02664057], [ -0.08147586, -0.02761816, -0.06328206, 0.07026077, -0.02661980]], "bond orders": [ , [ 1, 2, 1.4289], [ 1, 4, 0.0771], [ 1, 6, 1.4452], [ 1, 9, 0.9892], [ 1, 11, 0.0135], [ 2, 3, 1.4289], [ 2, 5, 0.0709], [ 2, 7, 0.0135], [ 2, 8, 0.0135], [ 2, 10, 0.9926], [ 3, 4, 1.4452], [ 3, 6, 0.0771], [ 3, 9, 0.0135], [ 3, 11, 0.9892], [ 4, 5, 1.4031], [ 4, 7, 0.9819], [ 4, 8, 0.0135], [ 4, 10, 0.0135], [ 4, 25, 0.0298], [ 5, 6, 1.4030], [ 5, 9, 0.0133], [ 5, 11, 0.0133], [ 5, 24, 1.0518], [ 5, 25, 0.0195], [ 5, 26, 0.0195], [ 6, 7, 0.0135], [ 6, 8, 0.9819], [ 6, 10, 0.0135], [ 6, 26, 0.0298], [ 12, 13, 1.4414], [ 12, 15, 0.0823], [ 12, 17, 1.4404], [ 12, 19, 0.0136], [ 12, 21, 0.9934], [ 12, 23, 0.0138], [ 13, 14, 1.4414], [ 13, 16, 0.0823], [ 13, 18, 0.0137], [ 13, 20, 0.0137], [ 13, 22, 0.9937], [ 14, 15, 1.4405], [ 14, 17, 0.0823], [ 14, 19, 0.0136], [ 14, 21, 0.0138], [ 14, 23, 0.9934], [ 15, 16, 1.4389], [ 15, 18, 0.9908], [ 15, 20, 0.0137], [ 15, 22, 0.0138], [ 16, 17, 1.4389], [ 16, 19, 0.9881], [ 16, 21, 0.0138], [ 16, 23, 0.0138], [ 17, 18, 0.0137], [ 17, 20, 0.9908], [ 17, 22, 0.0138], [ 24, 25, 1.6205], [ 24, 26, 1.6207], [ 25, 26, 0.1977]], "atomic dipole moments": [ [ 0.17817237, -0.08486467, -0.04392900], [ 0.14540861, 0.08417827, -0.04278264], [ 0.01511332, 0.19675971, -0.04389043], [ -0.13312254, 0.12935626, -0.04018292], [ 0.19288286, 0.11173317, -0.03496594], [ 0.04602572, -0.17971285, -0.04021404], [ 0.20153653, -0.11378295, 0.01052811], [ 0.00160042, 0.23134930, 0.01053943], [ -0.21014330, 0.11689540, 0.01051611], [ -0.20767197, -0.12027608, 0.01047094], [ -0.00330039, -0.24047911, 0.01050497], [ 0.14364790, -0.09442200, 0.04646228], [ 0.14775082, 0.08525506, 0.04574296], [ -0.00988717, 0.17152388, 0.04651218], [ -0.16085752, 0.07853975, 0.04618875], [ -0.15928291, -0.09201357, 0.04788960], [ -0.01237952, -0.17861850, 0.04614049], [ 0.20393913, -0.11931464, -0.00923317], [ 0.20084041, 0.11598812, -0.00705150], [ -0.00132604, 0.23622454, -0.00922251], [ -0.20820109, 0.11939647, -0.00910789], [ -0.20838147, -0.12034087, -0.00917493], [ -0.00072895, -0.23997078, -0.00911999], [ 0.08511339, 0.04958329, -0.01580055], [ 0.02008492, -0.59870284, 0.00147451], [ -0.50942425, 0.31508169, 0.00145541]], "atomic quadrupole moments": [ [ -0.23483260, 0.35458689, 0.08721839, 0.00404713, -0.00221582, 0.14761421], [ -0.31404269, -0.32538294, 0.07534445, -0.00036567, -0.00033284, 0.23869824], [ 0.32466627, 0.04769748, -0.47213648, 0.00021495, 0.00440101, 0.14747021], [ -0.20137605, 0.26534859, -0.05158060, 0.00369766, 0.01287493, 0.25295665], [ 0.07557700, 0.10609333, -0.02576532, 0.01046279, 0.00595898, -0.04981168], [ 0.14900317, 0.06774764, -0.40152994, 0.01311216, -0.00339044, 0.25252677], [ 0.01254889, 0.09029415, 0.04976636, -0.02624647, 0.01511978, -0.06231526], [ 0.11602428, 0.02847786, -0.05355800, 0.00002533, -0.03028812, -0.06246627], [ -0.02997061, 0.08898874, 0.07958685, 0.02520322, -0.01434626, -0.04961624], [ -0.02365008, -0.08660731, 0.07219455, 0.02550166, 0.01477689, -0.04854447], [ 0.12662694, -0.00399738, -0.07710619, 0.00009921, 0.02900232, -0.04952076], [ -0.30006940, 0.30202639, 0.09376142, -0.00114705, 0.00264928, 0.20630798], [ -0.28880250, -0.30941643, 0.08581319, 0.00000131, -0.00012030, 0.20298930], [ 0.26998302, -0.01227972, -0.47633316, 0.00185920, -0.00253625, 0.20635014], [ -0.27412905, 0.31742810, 0.07440885, 0.00468830, 0.00165078, 0.19972020], [ -0.28631949, -0.30807791, 0.08539979, 0.01417986, 0.00809755, 0.20091970], [ 0.27510342, 0.01535060, -0.47444771, 0.00389347, 0.00302610, 0.19934429], [ -0.02455963, 0.08953758, 0.07142463, 0.01809144, -0.01319294, -0.04686500], [ -0.02258736, -0.08556863, 0.07278918, 0.01619300, 0.00935858, -0.05020182], [ 0.12238760, 0.00168068, -0.07550214, -0.00241218, 0.02224940, -0.04688547], [ -0.03381135, 0.09231522, 0.07534668, -0.02181480, 0.01271313, -0.04153533], [ -0.03241315, -0.09470785, 0.07339190, -0.02201384, -0.01270961, -0.04097875], [ 0.12541539, -0.00265213, -0.08381623, 0.00011766, -0.02524766, -0.04159916], [ -0.02351376, -0.17170182, 0.20003381, 0.02815354, 0.01628303, -0.17652005], [ -0.68178231, -0.07559419, 1.00107233, -0.00398393, -0.00629851, -0.31929002], [ 0.52214226, -0.59650562, -0.20281034, -0.00741448, -0.00034301, -0.31933192]], "number of molecular orbitals": 250, "number of electrons": 76, "number of unpaired electrons": 0, "orbital energies / eV": [ -39.00848045, -30.92408173, -29.27753379, -27.99909431, -25.90152418, -24.80824514, -23.90248768, -23.87258388, -23.05138303, -20.97789424, -20.48867211, -20.12048257, -20.11544364, -18.76695942, -17.47736764, -17.34381024, -17.20541071, -17.07185189, -16.08872553, -15.84927455, -15.84807800, -15.65614615, -15.21613067, -14.56330637, -14.54742452, -13.73007911, -13.71561491, -13.08574752, -12.85114162, -12.41314585, -12.40267379, -11.72705663, -11.59086129, -11.00644510, -10.78721567, -10.74119348, -9.98685133, -9.97408150, -0.65042850, 0.98369714, 1.73651469, 1.79974353, 2.78340727, 3.33694685, 4.21809892, 5.47513054], "fractional occupation": [ 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 2.00000000, 0.00000000, 0.00000000, 0.00000000, 0.00000000, 0.00000000, 0.00000000, 0.00000000, 0.00000000], "program call": "xtb_dev benzene_dimer.xyz --ptb --json", "method": "PTB", "xtb version": "6.7.1 (1779d8a)" } The output as well as the ``JSON`` file contain the following properties: - orbital energies and occupations - atomic partial charges - shell populations - Wiberg bond orders - molecular dipole moment - molecular quadrupole tensor Vibrational spectroscopy ============================ Infrared and Raman intensity calculations for vibrational spectroscopy are additional applications of PTB. An example is the spectrum of endothelin (1EDN). In all spectra, the notation "Method\ **X** [Method\ **Y**]" indicates that frequencies were computed with Method\ **Y** and intensities with Method\ **X**. Within ``xtb``, this procedure is fully automated and requires no additional user input when using the CLI command below. .. figure:: ../figures/ptb_raman_1edn.png :width: 50% :align: center :alt: Raman activities of the polypeptide endothelin (327 atoms) computed by :math:`{\omega}`\ B97X-3c [GFN2-xTB] and PTB [GFN2-xTB]. The notation indicates that intensities were calculated with PTB or :math:`{\omega}`\ B97X-3c, while frequencies were computed with GFN2-xTB. In this example, Raman activities instead of Raman scattering cross-sections (== intensities) are plotted. Raman activities of the polypeptide endothelin (327 atoms) computed by :math:`{\omega}`\ B97X-3c [GFN2-xTB] and PTB [GFN2-xTB]. The notation indicates that intensities were calculated with PTB or :math:`{\omega}`\ B97X-3c, while frequencies were computed with GFN2-xTB. In this example, Raman activities instead of Raman scattering cross-sections (= intensities) are plotted. .. note:: Vibrational frequencies are not available with PTB! Instead, mixed GFN\ *n*-xTB and PTB spectra can be calculated. The following example shows the output of a vibrational spectrum calculation utilizing GFN2-xTB frequencies and PTB intensities. .. tab-set:: .. tab-item:: CLI input .. code-block:: none > xtb coord.xyz --ptb --hess --raman .. tab-item:: coord.xyz .. code-block:: none 12 C -1.21072 0.69984 -1.75114 C -1.21074 -0.69902 -1.75149 C 0.00072 -1.39843 -1.75114 C 1.21220 -0.69897 -1.75037 C 1.21222 0.69988 -1.74995 C 0.00077 1.39929 -1.75036 H 2.14941 -1.24008 -1.74839 H 2.14945 1.24099 -1.74755 H 0.00077 2.48148 -1.74837 H -2.14799 1.24091 -1.74971 H -2.14800 -1.24014 -1.75028 H 0.00066 -2.48066 -1.74972 .. tab-item:: vibspectrum .. code-block:: none $vibrational spectrum # mode symmetry wave number IR intensity Raman activity Raman scatt. cross-section selection rules # (cm⁻¹) (km*mol⁻¹) (Å⁴*amu⁻¹) (Ų*sr⁻¹) IR RAMAN 1 -0.00 0.00000 0.00000 0.00000E+00 - - 2 -0.00 0.00000 0.00000 0.00000E+00 - - 3 -0.00 0.00000 0.00000 0.00000E+00 - - 4 -0.00 0.00000 0.00000 0.00000E+00 - - 5 0.00 0.00000 0.00000 0.00000E+00 - - 6 0.00 0.00000 0.00000 0.00000E+00 - - 7 a 396.50 0.00000 0.00000 0.18961E-20 NO NO 8 a 396.53 0.00000 0.00000 0.33360E-20 NO NO 9 a 579.98 0.00000 1.54626 0.20949E-14 NO YES 10 a 580.02 0.00000 1.54429 0.20921E-14 NO YES 11 a 670.85 0.00000 0.00000 0.12043E-21 NO NO 12 a 701.48 126.55730 0.00015 0.16106E-18 YES NO 13 a 893.74 0.00061 0.23750 0.18585E-15 NO YES 14 a 893.79 0.00069 0.23627 0.18488E-15 NO YES 15 a 930.33 0.00000 0.00004 0.29258E-19 NO NO 16 a 930.39 0.00001 0.00004 0.31197E-19 NO NO 17 a 935.21 0.00000 0.00000 0.39056E-21 NO NO 18 a 954.09 0.00000 0.00000 0.18351E-22 NO NO 19 a 1025.26 0.00007 79.02989 0.52065E-13 NO YES 20 a 1070.03 15.31859 0.00001 0.35843E-20 YES NO 21 a 1070.11 15.26901 0.00001 0.40505E-20 YES NO 22 a 1170.72 0.00001 0.00004 0.21074E-19 NO NO 23 a 1186.56 0.00000 9.41232 0.51526E-14 NO YES 24 a 1186.60 0.00000 9.41073 0.51516E-14 NO YES 25 a 1233.84 0.00001 0.00000 0.93316E-21 NO NO 26 a 1305.43 0.00000 0.00001 0.72249E-20 NO NO 27 a 1431.72 18.20659 0.00001 0.28783E-20 YES NO 28 a 1431.79 18.18773 0.00001 0.28429E-20 YES NO 29 a 1542.28 0.00000 10.20802 0.39632E-14 NO YES 30 a 1542.41 0.00000 10.21628 0.39659E-14 NO YES 31 a 3048.92 0.00061 0.17889 0.24697E-16 NO YES 32 a 3052.31 0.00041 85.12880 0.11730E-13 NO YES 33 a 3052.40 0.00541 85.28612 0.11751E-13 NO YES 34 a 3063.56 22.28601 0.13306 0.18217E-16 YES YES 35 a 3063.68 22.38385 0.02186 0.29920E-17 YES YES 36 a 3071.51 0.00809 358.17986 0.48815E-13 NO YES $end In the shown example, omitting the ``--raman`` flag would result in a pure IR spectrum calculation (examples below). Similar to the basic usage example, also here, ``--json`` can be used to obtain the output (all components of the vibrational spectrum) in ``JSON`` format. .. figure:: ../figures/ptb_ir_spectra.png :width: 75% :align: center :alt: IR spectra of 3-pentenenitrile and 1-nitrosopyrrolidine. The experimental gas phase spectra and the spectra calculated with :math:`{\omega}`\ B97X-3c [GFN2-xTB], full GFN2-xTB, and PTB [GFN2-xTB] are shown. IR spectra of 3-pentenenitrile and 1-nitrosopyrrolidine. The experimental gas phase spectra and the spectra calculated with :math:`{\omega}`\ B97X-3c [GFN2-xTB], full GFN2-xTB, and PTB [GFN2-xTB] are shown.