1XTB(1)                                                                  XTB(1)
2
3
4

NAME

6       xtb - performs semiempirical quantummechanical calculations, for
7       version 6.0 and newer
8

SYNOPSIS

10       xtb [OPTIONS] FILE [OPTIONS]
11

DESCRIPTION

13       The xtb(1) program performs semiempirical quantummechanical
14       calculations. The underlying effective Hamiltonian is derived from
15       density functional tight binding (DFTB). This implementation of the xTB
16       Hamiltonian is currently compatible with the zeroth, first and second
17       level parametrisation for geometries, frequencies and non-covalent
18       interactions (GFN) as well as with the ionisation potential and
19       electron affinity (IPEA) parametrisation of the GFN1 Hamiltonian. The
20       generalized born (GB) model with solvent accessable surface area (SASA)
21       is also available available in this version. Ground state calculations
22       for the simplified Tamm-Danceoff approximation (sTDA) with the vTB
23       model are currently not implemented.
24
25   GEOMETRY INPUT
26       The wide variety of input formats for the geometry are supported by
27       using the mctc-lib. Supported formats are:
28
29       •   Xmol/xyz files (xyz, log)
30
31       •   Turbomole’s coord, riper’s periodic coord (tmol, coord)
32
33       •   DFTB+ genFormat geometry inputs as cluster, supercell or fractional
34           (gen)
35
36       •   VASP’s POSCAR/CONTCAR input files (vasp, poscar, contcar)
37
38       •   Protein Database files, only single files (pdb)
39
40       •   Connection table files, molfile (mol) and structure data format
41           (sdf)
42
43       •   Gaussian’s external program input (ein)
44
45       •   JSON input with qcschema_molecule or qcschema_input structure
46           (json)
47
48       •   FHI-AIMS' input files (geometry.in)
49
50       •   Q-Chem molecule block inputs (qchem)
51
52       For a full list visit:
53       https://grimme-lab.github.io/mctc-lib/page/index.html
54
55       xtb(1) reads additionally .CHRG and .UHF files if present.
56

INPUT SOURCES

58       xtb(1) gets its information from different sources. The one with
59       highest priority is the commandline with all allowed flags and
60       arguments described below. The secondary source is the xcontrol(7)
61       system, which can in principle use as many input files as wished. The
62       xcontrol(7) system is the successor of the set-block as present in
63       version 5.8.2 and earlier. This implementation of xtb(1) reads the
64       xcontrol(7) from two of three possible sources, the local xcontrol file
65       or the FILE used to specify the geometry and the global configuration
66       file found in the XTBPATH.
67

OPTIONS

69       -c, --chrg INT
70           specify molecular charge as INT, overrides .CHRG file and xcontrol
71           option
72
73       -u, --uhf INT
74           specify number of unpaired electrons as INT, overrides .UHF file
75           and xcontrol option
76
77       --gfn INT
78           specify parametrisation of GFN-xTB (default = 2)
79
80       --gfnff, --gff
81           specify parametrisation of GFN-FF
82
83       --oniom METHOD LIST
84           use subtractive embedding via ONIOM method. METHOD is given as
85           inner:outer where inner can be orca, turbomole, gfn2, gfn1, or
86           gfnff and outer can be gfn2, gfn1, or gfnff. The inner region is
87           given as a comma separated indices directly in the commandline or
88           in a file with each index on a separate line.
89
90       --etemp REAL
91           electronic temperature (default = 300K)
92
93       --esp
94           calculate electrostatic potential on VdW-grid
95
96       --stm
97           calculate STM image
98
99       -a, --acc REAL
100           accuracy for SCC calculation, lower is better (default = 1.0)
101
102       --vparam FILE
103           Parameter file for vTB calculation
104
105       --xparam FILE
106           Parameter file for xTB calculation (not used)
107
108       --alpb SOLVENT [STATE]
109           analytical linearized Poisson-Boltzmann (ALPB) model, available
110           solvents are acetone, acetonitrile, aniline, benzaldehyde, benzene,
111           ch2cl2, chcl3, cs2, dioxane, dmf, dmso, ether, ethylacetate,
112           furane, hexandecane, hexane, methanol, nitromethane, octanol,
113           woctanol, phenol, toluene, thf, water. The solvent input is not
114           case-sensitive. The Gsolv reference state can be chosen as
115           reference or bar1M (default).
116
117       -g, --gbsa SOLVENT [STATE]
118           generalized born (GB) model with solvent accessable surface (SASA)
119           model, available solvents are acetone, acetonitrile, benzene (only
120           GFN1-xTB), CH2Cl2, CHCl3, CS2, DMF (only GFN2-xTB), DMSO, ether,
121           H2O, methanol, n-hexane (only GFN2-xTB), THF and toluene. The
122           solvent input is not case-sensitive. The Gsolv reference state can
123           be chosen as reference or bar1M (default).
124
125       --cma
126           shifts molecule to center of mass and transforms cartesian
127           coordinates into the coordinate system of the principle axis (not
128           affected by ‘isotopes’-file).
129
130       --pop
131           requests printout of Mulliken population analysis
132
133       --molden
134           requests printout of molden file
135
136       --dipole
137           requests dipole printout
138
139       --wbo
140           requests Wiberg bond order printout
141
142       --lmo
143           requests localization of orbitals
144
145       --fod
146           requests FOD calculation
147
148   RUNTYPS
149           Note
150           You can only select one runtyp, only the first runtyp will be used
151           from the program, use implemented composite runtyps to perform
152           several operations at once.
153
154       --scc, --sp
155           performs a single point calculation
156
157       --vip
158           performs calculation of ionisation potential. This needs the
159           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
160
161       --vea
162           performs calculation of electron affinity. This needs the
163           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
164
165       --vipea
166           performs calculation of electron affinity and ionisation potential.
167           This needs the .param_ipea.xtb parameters and a GFN1 Hamiltonian.
168
169       --vfukui
170           performs calculation of Fukui indices.
171
172       --vomega
173           performs calculation of electrophilicity index. This needs the
174           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
175
176       --grad
177           performs a gradient calculation
178
179       -o, --opt [LEVEL]
180           call ancopt(3) to perform a geometry optimization, levels from
181           crude, sloppy, loose, normal (default), tight, verytight to extreme
182           can be chosen
183
184       --hess
185           perform a numerical hessian calculation on input geometry
186
187       --ohess [LEVEL]
188           perform a numerical hessian calculation on an ancopt(3) optimized
189           geometry
190
191       --bhess [LEVEL]
192           perform a biased numerical hessian calculation on an ancopt(3)
193           optimized geometry
194
195       --md
196           molecular dynamics simulation on start geometry
197
198       --metadyn [int]
199           meta dynamics simulation on start geometry, saving int snapshots of
200           the trajectory to bias the simulation
201
202       --omd
203           molecular dynamics simulation on ancopt(3) optimized geometry, a
204           loose optimization level will be chosen
205
206       --metaopt [LEVEL]
207           call ancopt(3) to perform a geometry optimization, then try to find
208           other minimas by meta dynamics
209
210       --path [FILE]
211           use meta dynamics to calculate a path from the input geometry to
212           the given product structure
213
214       --reactor
215           experimental
216
217       --modef INT
218           modefollowing algorithm. INT specifies the mode that should be used
219           for the modefollowing.
220
221   GENERAL
222       -I, --input FILE
223           use FILE as input source for xcontrol(7) instructions
224
225       --namespace STRING
226           give this xtb(1) run a namespace. All files, even temporary ones,
227           will be named according to STRING (might not work everywhere).
228
229       --[no]copy
230           copies the xcontrol file at startup (default = true)
231
232       --[no]restart
233           restarts calculation from xtbrestart (default = true)
234
235       -P, --parallel INT
236           number of parallel processes
237
238       --define
239           performs automatic check of input and terminate
240
241       --json
242           write xtbout.json file
243
244       --citation
245           print citation and terminate
246
247       --license
248           print license and terminate
249
250       -v, --verbose
251           be more verbose (not supported in every unit)
252
253       -s, --silent
254           clutter the screen less (not supported in every unit)
255
256       --ceasefiles
257           reduce the amount of output and files written
258
259       --strict
260           turns all warnings into hard errors
261
262       -h, --help
263           show help page
264

ENVIRONMENT VARIABLES

266       xtb(1) accesses a path-like variable to determine the location of its
267       parameter files, you have to provide the XTBPATH variable in the same
268       syntax as the system PATH variable. If this variable is not set, xtb(1)
269       will try to generate the XTBPATH from the deprecated XTBHOME variable.
270       In case the XTBHOME variable is not set it will be generated from the
271       HOME variable. So in principle storing the parameter files in the users
272       home directory is suffient but might lead to come cluttering.
273
274       Since the XTBHOME variable is deprecated with version 6.0 and newer
275       xtb(1) will issue a warning if XTBHOME is not part of the XTBPATH since
276       the XTBHOME variable is not used in production runs.
277

LOCAL FILES

279       xtb(1) accesses a number of local files in the current working
280       directory and also writes some output in specific files. Note that not
281       all input and output files allow the --namespace option.
282
283   INPUT
284       .CHRG
285           molecular charge as int
286
287       .UHF
288           Number of unpaired electrons as int
289
290       mdrestart
291           contains restart information for MD, --namespace compatible.
292
293       pcharge
294           point charge input, format is real real real real [int]. The first
295           real is used as partial charge, the next three entries are the
296           cartesian coordinates and the last is an optional atom type. Note
297           that the point charge input is not affected by a CMA
298           transformation. Also parallel Hessian calculations will fail due to
299           I/O errors when using point charge embedding.
300
301       xcontrol
302           default input file in --copy mode, see xcontrol(7) for details, set
303           by --input.
304
305       xtbrestart
306           contains restart information for SCC, --namespace compatible.
307
308   OUTPUT
309       charges
310           contains Mulliken partial charges calculated in SCC
311
312       wbo
313           contains Wiberg bond order calculated in SCC, --namespace
314           compatible.
315
316       energy
317           total energy in Turbomole format
318
319       gradient
320           geometry, energy and gradient in Turbomole format
321
322       hessian
323           contains the (not mass weighted) cartesian Hessian, --namespace
324           compatible.
325
326       xtbopt.xyz, xtbopt.coord
327           optimized geometry in the same format as the input geometry.
328
329       xtbhess.coord
330           distorted geometry if imaginary frequency was found
331
332       xtbopt.log
333           contains all structures obtained in the geometry optimization with
334           the respective energy in the comment line in a XMOL formatted
335           trajectory
336
337       xtbsiman.log,xtb.trj.int
338           trajectories from MD
339
340       scoord.int
341           coordinate dump of MD
342
343       fod.cub
344           FOD on a cube-type grid
345
346       spindensity.cub
347           spindensity on a cube-type grid
348
349       density.cub
350           density on a cube-type grid
351
352       molden.input
353           MOs and occupation for visualisation and sTDA-xTB calculations
354
355       pcgrad
356           gradient of the point charges
357
358       xtb_esp.cosmo
359           ESP fake cosmo output
360
361       xtb_esp_profile.dat
362           ESP histogramm data
363
364       vibspectrum
365           Turbomole style vibrational spectrum data group
366
367       g98.out, g98l.out, g98_canmode.out, g98_locmode.out
368           g98 fake output with normal or local modes
369
370       .tmpxtbmodef
371           input for mode following
372
373       coordprot.0
374           protonated species
375
376       xtblmoinfo
377           centers of the localized molecular orbitals
378
379       lmocent.coord
380           centers of the localized molecular orbitals
381
382       tmpxx
383           number of recommended modes for mode following
384
385       xtb_normalmodes, xtb_localmodes
386           binary dump for mode following
387
388   TOUCH
389       xtbmdok
390           generated by successful MD
391
392       .xtbok
393           generated after each successful xtb(1) run
394
395       .sccnotconverged
396           generated after failed SCC with printlevel=2
397

WARNINGS

399       xtb(1) can generate the two types of warnings, the first warning
400       section is printed immediately after the normal banner at startup,
401       summing up the evaluation of all input sources (commandline, xcontrol,
402       xtbrc). To check this warnings exclusively before running an expensive
403       calculation a input check is implemented via the --define flag. Please,
404       study this warnings carefully!
405
406       After xtb(1) has evaluated the all input sources it immediately enters
407       the production mode. Severe errors will lead to an abnormal termination
408       which is signalled by the printout to STDERR and a non-zero return
409       value (usually 128). All non-fatal errors are summerized in the end of
410       the calculation in one block, right bevor the timing analysis.
411
412       To aid the user to fix the problems generating these warnings a brief
413       summary of each warning with its respective string representation in
414       the output will be shown here:
415
416       ANCopt failed to converge the optimization
417           geometry optimization has failed to converge in the given number
418           optimization cycles. This is not neccessary a problem if only a
419           small number of cycles was given for the optimization on purpose.
420           All further calculations are done on the last geometry of the
421           optimization.
422
423       Hessian on incompletely optimized geometry!
424           This warning will be issued twice, once before the Hessian,
425           calculations starts (it would otherwise take some time before this
426           this warning could be detected) and in the warning block in the
427           end. The warning will be generated if the gradient norm on the
428           given geometry is higher than a certain threshold.
429

EXIT STATUS

431       0
432           normal termination of xtb(1)
433
434       128
435           Failure (termination via error stop generates 128 as return value)
436

BUGS

438       please report all bugs with an example input, --copy dump of internal
439       settings and the used geometry, as well as the --verbose output to
440       xtb@thch.uni-bonn.de
441

RESOURCES

443       Main web site: http://grimme.uni-bonn.de/software/xtb
444

COPYING

446       Copyright (C) 2015-2018 S. Grimme. For non-commerical, academia use
447       only.
448
449
450
451                                  2023-01-21                            XTB(1)
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