1XTB(1)                                                                  XTB(1)
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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 (6.1 only), first
17       and second level parametrisation for geometries, frequencies and
18       non-covalent interactions (GFN) as well as with the ionisation
19       potential and electron affinity (IPEA) parametrisation of the GFN1
20       Hamiltonian. The generalized born (GB) model with solvent accessable
21       surface area (SASA) is also available available in this version. Ground
22       state calculations for the simplified Tamm-Danceoff approximation
23       (sTDA) with the vTB model are currently not implemented.
24
25   GEOMETRY INPUT
26       The input coordinates can be presented in XMOL format and in Turbomole
27       format. For most calculations no specific changes to these formats have
28       to be made. The file type is determined automatically and the file
29       extension can be freely chosen. XMOL coordinates must be given in
30       Ångström, while in Turbomole format they can be given in Ångström as
31       well as in Bohr (default). The corresponding keyword is given in the
32       first line as ang or bohr instead of the $coord keyword.
33
34           Note
35           This implementation of xtb(1) can only identify and read coordinate
36           files in Turbomole, if the $coord is in the first line of the file,
37           valid Turbomole coordinate files with the $coord datagroup
38           elsewhere will not be read in correctly and lead to abnormal
39           termination of the program.
40
41       xtb(1) reads additionally .CHRG and .UHF files if present.
42

INPUT SOURCES

44       xtb(1) gets its information from different sources. The one with
45       highest priority is the commandline with all allowed flags and
46       arguments described below. The secondary source is the xcontrol(7)
47       system, which can in principle use as many input files as wished. The
48       xcontrol(7) system is the successor of the set-block as present in
49       version 5.8.2 and earlier. This implementation of xtb(1) reads the
50       xcontrol(7) from two of three possible sources, the local xcontrol file
51       or the FILE used to specify the geometry and the global configuration
52       file found in the XTBPATH.
53

OPTIONS

55       -c, --chrg INT
56           specify molecular charge as INT, overrides .CHRG file and xcontrol
57           option
58
59       -u, --uhf INT
60           specify Nalpha-Nbeta as INT, overrides .UHF file and xcontrol
61           option
62
63       --gfn INT
64           specify parametrisation of GFN-xTB (default = 2)
65
66       --gfnff, --gff
67           specify parametrisation of GFN-FF
68
69       --etemp REAL
70           electronic temperature (default = 300K)
71
72       --esp
73           calculate electrostatic potential on VdW-grid
74
75       --stm
76           calculate STM image
77
78       -a, --acc REAL
79           accuracy for SCC calculation, lower is better (default = 1.0)
80
81       --vparam FILE
82           Parameter file for vTB calculation
83
84       --xparam FILE
85           Parameter file for xTB calculation (not used)
86
87       --alpb SOLVENT [STATE]
88           analytical linearized Poisson-Boltzmann (ALPB) model, available
89           solvents are acetone, acetonitrile, aniline, benzaldehyde, benzene,
90           ch2cl2, chcl3, cs2, dioxane, dmf, dmso, ether, ethylacetate,
91           furane, hexandecane, hexane, methanol, nitromethane, octanol,
92           woctanol, phenol, toluene, thf, water. The solvent input is not
93           case-sensitive. The Gsolv reference state can be chosen as
94           reference or bar1M (default).
95
96       -g, --gbsa SOLVENT [STATE]
97           generalized born (GB) model with solvent accessable surface (SASA)
98           model, available solvents are acetone, acetonitrile, benzene (only
99           GFN1-xTB), CH2Cl2, CHCl3, CS2, DMF (only GFN2-xTB), DMSO, ether,
100           H2O, methanol, n-hexane (only GFN2-xTB), THF and toluene. The
101           solvent input is not case-sensitive. The Gsolv reference state can
102           be chosen as reference or bar1M (default).
103
104       --cma
105           shifts molecule to center of mass and transforms cartesian
106           coordinates into the coordinate system of the principle axis (not
107           affected by ‘isotopes’-file).
108
109       --pop
110           requests printout of Mulliken population analysis
111
112       --molden
113           requests printout of molden file
114
115       --dipole
116           requests dipole printout
117
118       --wbo
119           requests Wiberg bond order printout
120
121       --lmo
122           requests localization of orbitals
123
124       --fod
125           requests FOD calculation
126
127   RUNTYPS
128           Note
129           You can only select one runtyp, only the first runtyp will be used
130           from the program, use implemented composite runtyps to perform
131           several operations at once.
132
133       --scc, --sp
134           performs a single point calculation
135
136       --vip
137           performs calculation of ionisation potential. This needs the
138           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
139
140       --vea
141           performs calculation of electron affinity. This needs the
142           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
143
144       --vipea
145           performs calculation of electron affinity and ionisation potential.
146           This needs the .param_ipea.xtb parameters and a GFN1 Hamiltonian.
147
148       --vfukui
149           performs calculation of Fukui indices.
150
151       --vomega
152           performs calculation of electrophilicity index. This needs the
153           .param_ipea.xtb parameters and a GFN1 Hamiltonian.
154
155       --grad
156           performs a gradient calculation
157
158       -o, --opt [LEVEL]
159           call ancopt(3) to perform a geometry optimization, levels from
160           crude, sloppy, loose, normal (default), tight, verytight to extreme
161           can be chosen
162
163       --hess
164           perform a numerical hessian calculation on input geometry
165
166       --ohess [LEVEL]
167           perform a numerical hessian calculation on an ancopt(3) optimized
168           geometry
169
170       --bhess [LEVEL]
171           perform a biased numerical hessian calculation on an ancopt(3)
172           optimized geometry
173
174       --md
175           molecular dynamics simulation on start geometry
176
177       --metadyn [int]
178           meta dynamics simulation on start geometry, saving int snapshots of
179           the trajectory to bias the simulation (6.1 only)
180
181       --omd
182           molecular dynamics simulation on ancopt(3) optimized geometry, a
183           loose optimization level will be chosen
184
185       --metaopt [LEVEL]
186           call ancopt(3) to perform a geometry optimization, then try to find
187           other minimas by meta dynamics (6.1 only)
188
189       --path [FILE]
190           use meta dynamics to calculate a path from the input geometry to
191           the given product structure (6.1 only)
192
193       --reactor
194           experimental (6.1 only)
195
196       --modef INT
197           modefollowing algorithm. INT specifies the mode that should be used
198           for the modefollowing.
199
200   GENERAL
201       -I, --input FILE
202           use FILE as input source for xcontrol(7) instructions
203
204       --namespace STRING
205           give this xtb(1) run a namespace. All files, even temporary ones,
206           will be named according to STRING (might not work everywhere).
207
208       --[no]copy
209           copies the xcontrol file at startup (default = true)
210
211       --[no]restart
212           restarts calculation from xtbrestart (default = true)
213
214       -P, --parallel INT
215           number of parallel processes
216
217       --define
218           performs automatic check of input and terminate
219
220       --json
221           write xtbout.json file
222
223       --citation
224           print citation and terminate
225
226       --license
227           print license and terminate
228
229       -v, --verbose
230           be more verbose (not supported in every unit)
231
232       -s, --silent
233           clutter the screen less (not supported in every unit)
234
235       --ceasefiles
236           reduce the amount of output and files written
237
238       --strict
239           turns all warnings into hard errors
240
241       -h, --help
242           show help page
243

ENVIRONMENT VARIABLES

245       xtb(1) accesses a path-like variable to determine the location of its
246       parameter files, you have to provide the XTBPATH variable in the same
247       syntax as the system PATH variable. If this variable is not set, xtb(1)
248       will try to generate the XTBPATH from the deprecated XTBHOME variable.
249       In case the XTBHOME variable is not set it will be generated from the
250       HOME variable. So in principle storing the parameter files in the users
251       home directory is suffient but might lead to come cluttering.
252
253       Since the XTBHOME variable is deprecated with version 6.0 and newer
254       xtb(1) will issue a warning if XTBHOME is not part of the XTBPATH since
255       the XTBHOME variable is not used in production runs.
256

LOCAL FILES

258       xtb(1) accesses a number of local files in the current working
259       directory and also writes some output in specific files. Note that not
260       all input and output files allow the --namespace option.
261
262   INPUT
263       .CHRG
264           molecular charge as int
265
266       .UHF
267           Nalpha-Nbeta as int
268
269       mdrestart
270           contains restart information for MD, --namespace compatible.
271
272       pcharge
273           point charge input, format is real real real real [int]. The first
274           real is used as partial charge, the next three entries are the
275           cartesian coordinates and the last is an optional atom type. Note
276           that the point charge input is not affected by a CMA
277           transformation. Also parallel Hessian calculations will fail due to
278           I/O errors when using point charge embedding.
279
280       solvent
281           qmdff(1) input file
282
283       xcontrol
284           default input file in --copy mode, see xcontrol(7) for details, set
285           by --input.
286
287       xtbrestart
288           contains restart information for SCC, --namespace compatible.
289
290   OUTPUT
291       charges
292           contains Mulliken partial charges calculated in SCC
293
294       wbo
295           contains Wiberg bond order calculated in SCC, --namespace
296           compatible.
297
298       energy
299           total energy in Turbomole format
300
301       gradient
302           geometry, energy and gradient in Turbomole format
303
304       hessian
305           contains the (not mass weighted) cartesian Hessian, --namespace
306           compatible.
307
308       xtbopt.xyz, xtbopt.coord
309           optimized geometry in the same format as the input geometry.
310
311       xtbhess.coord
312           distorted geometry if imaginary frequency was found
313
314       xtbopt.log
315           contains all structures obtained in the geometry optimization with
316           the respective energy in the comment line in a XMOL formatted
317           trajectory
318
319       xtbsiman.log,xtb.trj.int
320           trajectories from MD
321
322       scoord.int
323           coordinate dump of MD
324
325       fod.cub
326           FOD on a cube-type grid
327
328       spindensity.cub
329           spindensity on a cube-type grid
330
331       density.cub
332           density on a cube-type grid
333
334       molden.input
335           MOs and occupation for visualisation and sTDA-xTB calculations
336
337       pcgrad
338           gradient of the point charges
339
340       xtb_esp.cosmo
341           ESP fake cosmo output
342
343       xtb_esp_profile.dat
344           ESP histogramm data
345
346       vibspectrum
347           Turbomole style vibrational spectrum data group
348
349       g98.out, g98l.out, g98_canmode.out, g98_locmode.out
350           g98 fake output with normal or local modes
351
352       .tmpxtbmodef
353           input for mode following
354
355       coordprot.0
356           protonated species
357
358       xtblmoinfo
359           centers of the localized molecular orbitals
360
361       lmocent.coord
362           centers of the localized molecular orbitals
363
364       tmpxx
365           number of recommended modes for mode following
366
367       xtb_normalmodes, xtb_localmodes
368           binary dump for mode following
369
370   TOUCH
371       xtbmdok
372           generated by successful MD
373
374       .xtbok
375           generated after each successful xtb(1) run
376
377       .sccnotconverged
378           generated after failed SCC with printlevel=2
379

WARNINGS

381       xtb(1) can generate the two types of warnings, the first warning
382       section is printed immediately after the normal banner at startup,
383       summing up the evaluation of all input sources (commandline, xcontrol,
384       xtbrc). To check this warnings exclusively before running an expensive
385       calculation a input check is implemented via the --define flag. Please,
386       study this warnings carefully!
387
388       After xtb(1) has evaluated the all input sources it immediately enters
389       the production mode. Severe errors will lead to an abnormal termination
390       which is signalled by the printout to STDERR and a non-zero return
391       value (usually 128). All non-fatal errors are summerized in the end of
392       the calculation in one block, right bevor the timing analysis.
393
394       To aid the user to fix the problems generating these warnings a brief
395       summary of each warning with its respective string representation in
396       the output will be shown here:
397
398       ANCopt failed to converge the optimization
399           geometry optimization has failed to converge in the given number
400           optimization cycles. This is not neccessary a problem if only a
401           small number of cycles was given for the optimization on purpose.
402           All further calculations are done on the last geometry of the
403           optimization.
404
405       Hessian on incompletely optimized geometry!
406           This warning will be issued twice, once before the Hessian,
407           calculations starts (it would otherwise take some time before this
408           this warning could be detected) and in the warning block in the
409           end. The warning will be generated if the gradient norm on the
410           given geometry is higher than a certain threshold.
411

EXIT STATUS

413       0
414           normal termination of xtb(1)
415
416       128
417           Failure (termination via error stop generates 128 as return value)
418

BUGS

420       please report all bugs with an example input, --copy dump of internal
421       settings and the used geometry, as well as the --verbose output to
422       xtb@thch.uni-bonn.de
423

RESOURCES

425       Main web site: http://grimme.uni-bonn.de/software/xtb
426

COPYING

428       Copyright (C) 2015-2018 S. Grimme. For non-commerical, academia use
429       only.
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432
433                                  2021-07-23                            XTB(1)
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