Provided by: xtb_6.6.1-1_amd64 
NAME
xtb - performs semiempirical quantummechanical calculations, for version 6.0 and newer
SYNOPSIS
xtb [OPTIONS] FILE [OPTIONS]
DESCRIPTION
The xtb(1) program performs semiempirical quantummechanical calculations. The underlying effective
Hamiltonian is derived from density functional tight binding (DFTB). This implementation of the xTB
Hamiltonian is currently compatible with the zeroth, first and second level parametrisation for
geometries, frequencies and non-covalent interactions (GFN) as well as with the ionisation potential and
electron affinity (IPEA) parametrisation of the GFN1 Hamiltonian. The generalized born (GB) model with
solvent accessable surface area (SASA) is also available in this version. Ground state calculations for
the simplified Tamm-Dancoff approximation (sTDA) with the vTB model are currently not implemented.
GEOMETRY INPUT
The wide variety of input formats for the geometry are supported by using the mctc-lib. Supported formats
are:
• Xmol/xyz files (xyz, log)
• Turbomole’s coord, riper’s periodic coord (tmol, coord)
• DFTB+ genFormat geometry inputs as cluster, supercell or fractional (gen)
• VASP’s POSCAR/CONTCAR input files (vasp, poscar, contcar)
• Protein Database files, only single files (pdb)
• Connection table files, molfile (mol) and structure data format (sdf)
• Gaussian’s external program input (ein)
• JSON input with qcschema_molecule or qcschema_input structure (json)
• FHI-AIMS' input files (geometry.in)
• Q-Chem molecule block inputs (qchem)
For a full list visit: https://grimme-lab.github.io/mctc-lib/page/index.html
xtb(1) reads additionally .CHRG and .UHF files if present.
INPUT SOURCES
xtb(1) gets its information from different sources. The one with highest priority is the commandline with
all allowed flags and arguments described below. The secondary source is the xcontrol(7) system, which
can in principle use as many input files as wished. The xcontrol(7) system is the successor of the
set-block as present in version 5.8.2 and earlier. This implementation of xtb(1) reads the xcontrol(7)
from two of three possible sources, the local xcontrol file or the FILE used to specify the geometry and
the global configuration file found in the XTBPATH.
OPTIONS
-c, --chrg INT
specify molecular charge as INT, overrides .CHRG file and xcontrol option
-c, --chrg INT:INT
specify charges for inner region:outer region for oniom calculation, overrides .CHRG file and
xcontrol option
-u, --uhf INT
specify number of unpaired electrons as INT, overrides .UHF file and xcontrol option
--gfn INT
specify parametrisation of GFN-xTB (default = 2)
--gfnff, --gff
specify parametrisation of GFN-FF
--tblite
use tblite library as implementation for xTB
--spinpol
enables spin-polarization for xTB methods (tblite required)
--oniom METHOD LIST
use subtractive embedding via ONIOM method. METHOD is given as high:low where high can be orca,
turbomole, gfn2, gfn1, or gfnff and low can be gfn2, gfn1, or gfnff. The inner region is given as
comma-separated indices directly in the commandline or in a file with each index on a separate line.
--etemp REAL
electronic temperature (default = 300K)
--esp
calculate electrostatic potential on VdW-grid
--stm
calculate STM image
-a, --acc REAL
accuracy for SCC calculation, lower is better (default = 1.0)
--vparam FILE
Parameter file for xTB calculation
--alpb SOLVENT [STATE]
analytical linearized Poisson-Boltzmann (ALPB) model, available solvents are acetone, acetonitrile,
aniline, benzaldehyde, benzene, ch2cl2, chcl3, cs2, dioxane, dmf, dmso, ether, ethylacetate, furane,
hexandecane, hexane, methanol, nitromethane, octanol, woctanol, phenol, toluene, thf, water. The
solvent input is not case-sensitive. The Gsolv reference state can be chosen as reference or bar1M
(default).
-g, --gbsa SOLVENT [STATE]
generalized born (GB) model with solvent accessable surface (SASA) model, available solvents are
acetone, acetonitrile, benzene (only GFN1-xTB), CH2Cl2, CHCl3, CS2, DMF (only GFN2-xTB), DMSO, ether,
H2O, methanol, n-hexane (only GFN2-xTB), THF and toluene. The solvent input is not case-sensitive.
The Gsolv reference state can be chosen as reference or bar1M (default).
--cma
shifts molecule to center of mass and transforms cartesian coordinates into the coordinate system of
the principle axis (not affected by ‘isotopes’-file).
--pop
requests printout of Mulliken population analysis
--molden
requests printout of molden file
--dipole
requests dipole printout
--wbo
requests Wiberg bond order printout
--lmo
requests localization of orbitals
--fod
requests FOD calculation
RUNTYPS
Note
You can only select one runtyp, only the first runtyp will be used from the program, use implemented
composite runtyps to perform several operations at once.
--scc, --sp
performs a single point calculation
--vip
performs calculation of ionisation potential. This needs the .param_ipea.xtb parameters and a GFN1
Hamiltonian.
--vea
performs calculation of electron affinity. This needs the .param_ipea.xtb parameters and a GFN1
Hamiltonian.
--vipea
performs calculation of electron affinity and ionisation potential. This needs the .param_ipea.xtb
parameters and a GFN1 Hamiltonian.
--vfukui
performs calculation of Fukui indices.
--vomega
performs calculation of electrophilicity index. This needs the .param_ipea.xtb parameters and a GFN1
Hamiltonian.
--grad
performs a gradient calculation
-o, --opt [LEVEL]
call ancopt(3) to perform a geometry optimization, levels from crude, sloppy, loose, normal
(default), tight, verytight to extreme can be chosen
--hess
perform a numerical hessian calculation on input geometry
--ohess [LEVEL]
perform a numerical hessian calculation on an ancopt(3) optimized geometry
--bhess [LEVEL]
perform a biased numerical hessian calculation on an ancopt(3) optimized geometry
--md
molecular dynamics simulation on start geometry
--metadyn [int]
meta dynamics simulation on start geometry, saving int snapshots of the trajectory to bias the
simulation
--omd
molecular dynamics simulation on ancopt(3) optimized geometry, a loose optimization level will be
chosen
--metaopt [LEVEL]
call ancopt(3) to perform a geometry optimization, then try to find other minimas by meta dynamics
--path [FILE]
use meta dynamics to calculate a path from the input geometry to the given product structure
--reactor
experimental
--modef INT
modefollowing algorithm. INT specifies the mode that should be used for the modefollowing.
GENERAL
-I, --input FILE
use FILE as input source for xcontrol(7) instructions
--namespace STRING
give this xtb(1) run a namespace. All files, even temporary ones, will be named according to STRING
(might not work everywhere).
--[no]copy
copies the xcontrol file at startup (default = true)
--[no]restart
restarts calculation from xtbrestart (default = true)
-P, --parallel INT
number of parallel processes
--define
performs automatic check of input and terminate
--json
write xtbout.json file
--citation
print citation and terminate
--license
print license and terminate
-v, --verbose
be more verbose (not supported in every unit)
-s, --silent
clutter the screen less (not supported in every unit)
--ceasefiles
reduce the amount of output and files written
--strict
turns all warnings into hard errors
-h, --help
show help page
--cut
create inner region for oniom calculation without performing any calcultion
ENVIRONMENT VARIABLES
xtb(1) accesses a path-like variable to determine the location of its parameter files, you have to
provide the XTBPATH variable in the same syntax as the system PATH variable. If this variable is not set,
xtb(1) will try to generate the XTBPATH from the deprecated XTBHOME variable. In case the XTBHOME
variable is not set it will be generated from the HOME variable. So in principle storing the parameter
files in the users home directory is suffient but might lead to come cluttering.
Since the XTBHOME variable is deprecated with version 6.0 and newer xtb(1) will issue a warning if
XTBHOME is not part of the XTBPATH since the XTBHOME variable is not used in production runs.
LOCAL FILES
xtb(1) accesses a number of local files in the current working directory and also writes some output in
specific files. Note that not all input and output files allow the --namespace option.
INPUT
.CHRG
molecular charge as int
.UHF
Number of unpaired electrons as int
mdrestart
contains restart information for MD, --namespace compatible.
pcharge
point charge input, format is real real real real [int]. The first real is used as partial charge,
the next three entries are the cartesian coordinates and the last is an optional atom type. Note that
the point charge input is not affected by a CMA transformation. Also parallel Hessian calculations
will fail due to I/O errors when using point charge embedding.
xcontrol
default input file in --copy mode, see xcontrol(7) for details, set by --input.
xtbrestart
contains restart information for SCC, --namespace compatible.
OUTPUT
charges
contains Mulliken partial charges calculated in SCC
wbo
contains Wiberg bond order calculated in SCC, --namespace compatible.
energy
total energy in Turbomole format
gradient
geometry, energy and gradient in Turbomole format
hessian
contains the (not mass weighted) cartesian Hessian, --namespace compatible.
xtbopt.xyz, xtbopt.coord
optimized geometry in the same format as the input geometry.
xtbhess.coord
distorted geometry if imaginary frequency was found
xtbopt.log
contains all structures obtained in the geometry optimization with the respective energy in the
comment line in a XMOL formatted trajectory
xtbsiman.log,xtb.trj.int
trajectories from MD
scoord.int
coordinate dump of MD
fod.cub
FOD on a cube-type grid
spindensity.cub
spindensity on a cube-type grid
density.cub
density on a cube-type grid
molden.input
MOs and occupation for visualisation and sTDA-xTB calculations
pcgrad
gradient of the point charges
xtb_esp.cosmo
ESP fake cosmo output
xtb_esp_profile.dat
ESP histogramm data
vibspectrum
Turbomole style vibrational spectrum data group
g98.out, g98l.out, g98_canmode.out, g98_locmode.out
g98 fake output with normal or local modes
.tmpxtbmodef
input for mode following
coordprot.0
protonated species
xtblmoinfo
centers of the localized molecular orbitals
lmocent.coord
centers of the localized molecular orbitals
tmpxx
number of recommended modes for mode following
xtb_normalmodes, xtb_localmodes
binary dump for mode following
TOUCH
xtbmdok
generated by successful MD
.xtbok
generated after each successful xtb(1) run
.sccnotconverged
generated after failed SCC with printlevel=2
WARNINGS
xtb(1) can generate the two types of warnings, the first warning section is printed immediately after the
normal banner at startup, summing up the evaluation of all input sources (commandline, xcontrol, xtbrc).
To check this warnings exclusively before running an expensive calculation a input check is implemented
via the --define flag. Please, study this warnings carefully!
After xtb(1) has evaluated the all input sources it immediately enters the production mode. Severe errors
will lead to an abnormal termination which is signalled by the printout to STDERR and a non-zero return
value (usually 128). All non-fatal errors are summerized in the end of the calculation in one block,
right before the timing analysis.
To aid the user to fix the problems generating these warnings a brief summary of each warning with its
respective string representation in the output will be shown here:
ANCopt failed to converge the optimization
geometry optimization has failed to converge in the given number optimization cycles. This is not
neccessary a problem if only a small number of cycles was given for the optimization on purpose. All
further calculations are done on the last geometry of the optimization.
Hessian on incompletely optimized geometry!
This warning will be issued twice, once before the Hessian, calculations starts (it would otherwise
take some time before this this warning could be detected) and in the warning block in the end. The
warning will be generated if the gradient norm on the given geometry is higher than a certain
threshold.
EXIT STATUS
0
normal termination of xtb(1)
128
Failure (termination via error stop generates 128 as return value)
BUGS
please report all bugs with an example input, --copy dump of internal settings and the used geometry, as
well as the --verbose output to xtb@thch.uni-bonn.de
RESOURCES
Main web site: http://grimme.uni-bonn.de/software/xtb
COPYING
Copyright © 2017-2023 Stefan Grimme
xtb is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General
Public License as published by the Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
xtb is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
License for more details.
You should have received a copy of the GNU Lesser General Public License along with xtb. If not, see
https://www.gnu.org/licenses/.
08/07/2023 XTB(1)