'\" t
.\"     Title: xtb
.\"    Author: [FIXME: author] [see http://www.docbook.org/tdg5/en/html/author]
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 03/29/2023
.\"    Manual: \ \&
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "XTB" "1" "03/29/2023" "\ \&" "\ \&"
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.SH "NAME"
xtb \- performs semiempirical quantummechanical calculations, for version 6\&.0 and newer
.SH "SYNOPSIS"
.sp
\fBxtb\fR [\fIOPTIONS\fR] \fIFILE\fR [\fIOPTIONS\fR]
.SH "DESCRIPTION"
.sp
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\&.
.SS "GEOMETRY INPUT"
.sp
The wide variety of input formats for the geometry are supported by using the mctc\-lib\&. Supported formats are:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Xmol/xyz files (xyz, log)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Turbomole\(cqs coord, riper\(cqs periodic coord (tmol, coord)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
DFTB+ genFormat geometry inputs as cluster, supercell or fractional (gen)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
VASP\(cqs POSCAR/CONTCAR input files (vasp, poscar, contcar)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Protein Database files, only single files (pdb)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Connection table files, molfile (mol) and structure data format (sdf)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Gaussian\(cqs external program input (ein)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
JSON input with
qcschema_molecule
or
qcschema_input
structure (json)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
FHI\-AIMS\*(Aq input files (geometry\&.in)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
Q\-Chem molecule block inputs (qchem)
.RE
.sp
For a full list visit: https://grimme\-lab\&.github\&.io/mctc\-lib/page/index\&.html
.sp
xtb(1) reads additionally \&.CHRG and \&.UHF files if present\&.
.SH "INPUT SOURCES"
.sp
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 \fIFILE\fR used to specify the geometry and the global configuration file found in the XTBPATH\&.
.SH "OPTIONS"
.PP
\fB\-c, \-\-chrg\fR \fIINT\fR
.RS 4
specify molecular charge as
\fIINT\fR, overrides
\&.CHRG
file and
xcontrol
option
.RE
.PP
\fB\-c, \-\-chrg\fR \fIINT:INT\fR
.RS 4
specify charges for
\fIinner region:outer region\fR
for
oniom
calculation, overrides
\&.CHRG
file and
xcontrol
option
.RE
.PP
\fB\-u, \-\-uhf\fR \fIINT\fR
.RS 4
specify number of unpaired electrons as
\fIINT\fR, overrides
\&.UHF
file and
xcontrol
option
.RE
.PP
\fB\-\-gfn\fR \fIINT\fR
.RS 4
specify parametrisation of GFN\-xTB (default = 2)
.RE
.PP
\fB\-\-gfnff, \-\-gff\fR
.RS 4
specify parametrisation of GFN\-FF
.RE
.PP
\fB\-\-tblite\fR
.RS 4
use tblite library as implementation of for xTB
.RE
.PP
\fB\-\-oniom\fR \fIMETHOD\fR \fILIST\fR
.RS 4
use subtractive embedding via ONIOM method\&.
\fIMETHOD\fR
is given as
high:low
where
high
can be
\fIorca\fR,
\fIturbomole\fR,
\fIgfn2\fR,
\fIgfn1\fR, or
\fIgfnff\fR
and
low
can be
\fIgfn2\fR,
\fIgfn1\fR, or
\fIgfnff\fR\&. The inner region is given as comma\-separated indices directly in the commandline or in a file with each index on a separate line\&.
.RE
.PP
\fB\-\-etemp\fR \fIREAL\fR
.RS 4
electronic temperature (default = 300K)
.RE
.PP
\fB\-\-esp\fR
.RS 4
calculate electrostatic potential on VdW\-grid
.RE
.PP
\fB\-\-stm\fR
.RS 4
calculate STM image
.RE
.PP
\fB\-a, \-\-acc\fR \fIREAL\fR
.RS 4
accuracy for SCC calculation, lower is better (default = 1\&.0)
.RE
.PP
\fB\-\-vparam\fR \fIFILE\fR
.RS 4
Parameter file for xTB calculation
.RE
.PP
\fB\-\-alpb\fR \fISOLVENT\fR [\fISTATE\fR]
.RS 4
analytical linearized Poisson\-Boltzmann (ALPB) model, available solvents are
\fIacetone\fR,
\fIacetonitrile\fR,
\fIaniline\fR,
\fIbenzaldehyde\fR,
\fIbenzene\fR,
\fIch2cl2\fR,
\fIchcl3\fR,
\fIcs2\fR,
\fIdioxane\fR,
\fIdmf\fR,
\fIdmso\fR,
\fIether\fR,
\fIethylacetate\fR,
\fIfurane\fR,
\fIhexandecane\fR,
\fIhexane\fR,
\fImethanol\fR,
\fInitromethane\fR,
\fIoctanol\fR,
\fIwoctanol\fR,
\fIphenol\fR,
\fItoluene\fR,
\fIthf\fR,
\fIwater\fR\&. The solvent input is not case\-sensitive\&. The Gsolv reference state can be chosen as
\fIreference\fR
or
\fIbar1M\fR
(default)\&.
.RE
.PP
\fB\-g, \-\-gbsa\fR \fISOLVENT\fR [\fISTATE\fR]
.RS 4
generalized born (GB) model with solvent accessable surface (SASA) model, available solvents are
\fIacetone\fR,
\fIacetonitrile\fR,
\fIbenzene\fR
(only GFN1\-xTB),
\fICH2Cl2\fR,
\fICHCl3\fR,
\fICS2\fR,
\fIDMF\fR
(only GFN2\-xTB),
\fIDMSO\fR,
\fIether\fR,
\fIH2O\fR,
\fImethanol\fR,
\fIn\-hexane\fR
(only GFN2\-xTB),
\fITHF\fR
and
\fItoluene\fR\&. The solvent input is not case\-sensitive\&. The Gsolv reference state can be chosen as
\fIreference\fR
or
\fIbar1M\fR
(default)\&.
.RE
.PP
\fB\-\-cma\fR
.RS 4
shifts molecule to center of mass and transforms cartesian coordinates into the coordinate system of the principle axis (not affected by \(oqisotopes\(cq\-file)\&.
.RE
.PP
\fB\-\-pop\fR
.RS 4
requests printout of Mulliken population analysis
.RE
.PP
\fB\-\-molden\fR
.RS 4
requests printout of molden file
.RE
.PP
\fB\-\-dipole\fR
.RS 4
requests dipole printout
.RE
.PP
\fB\-\-wbo\fR
.RS 4
requests Wiberg bond order printout
.RE
.PP
\fB\-\-lmo\fR
.RS 4
requests localization of orbitals
.RE
.PP
\fB\-\-fod\fR
.RS 4
requests FOD calculation
.RE
.SS "RUNTYPS"
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
.sp
You can only select \fBone\fR runtyp, only the first runtyp will be used from the program, use implemented composite runtyps to perform several operations at once\&.
.sp .5v
.RE
.PP
\fB\-\-scc, \-\-sp\fR
.RS 4
performs a single point calculation
.RE
.PP
\fB\-\-vip\fR
.RS 4
performs calculation of ionisation potential\&. This needs the \&.param_ipea\&.xtb parameters and a GFN1 Hamiltonian\&.
.RE
.PP
\fB\-\-vea\fR
.RS 4
performs calculation of electron affinity\&. This needs the \&.param_ipea\&.xtb parameters and a GFN1 Hamiltonian\&.
.RE
.PP
\fB\-\-vipea\fR
.RS 4
performs calculation of electron affinity and ionisation potential\&. This needs the \&.param_ipea\&.xtb parameters and a GFN1 Hamiltonian\&.
.RE
.PP
\fB\-\-vfukui\fR
.RS 4
performs calculation of Fukui indices\&.
.RE
.PP
\fB\-\-vomega\fR
.RS 4
performs calculation of electrophilicity index\&. This needs the \&.param_ipea\&.xtb parameters and a GFN1 Hamiltonian\&.
.RE
.PP
\fB\-\-grad\fR
.RS 4
performs a gradient calculation
.RE
.PP
\fB\-o, \-\-opt\fR [\fILEVEL\fR]
.RS 4
call
ancopt(3)
to perform a geometry optimization, levels from crude, sloppy, loose, normal (default), tight, verytight to extreme can be chosen
.RE
.PP
\fB\-\-hess\fR
.RS 4
perform a numerical hessian calculation on input geometry
.RE
.PP
\fB\-\-ohess\fR [\fILEVEL\fR]
.RS 4
perform a numerical hessian calculation on an
ancopt(3)
optimized geometry
.RE
.PP
\fB\-\-bhess\fR [\fILEVEL\fR]
.RS 4
perform a biased numerical hessian calculation on an
ancopt(3)
optimized geometry
.RE
.PP
\fB\-\-md\fR
.RS 4
molecular dynamics simulation on start geometry
.RE
.PP
\fB\-\-metadyn\fR [\fIint\fR]
.RS 4
meta dynamics simulation on start geometry, saving
\fIint\fR
snapshots of the trajectory to bias the simulation
.RE
.PP
\fB\-\-omd\fR
.RS 4
molecular dynamics simulation on
ancopt(3)
optimized geometry, a loose optimization level will be chosen
.RE
.PP
\fB\-\-metaopt\fR [\fILEVEL\fR]
.RS 4
call
ancopt(3)
to perform a geometry optimization, then try to find other minimas by meta dynamics
.RE
.PP
\fB\-\-path\fR [\fIFILE\fR]
.RS 4
use meta dynamics to calculate a path from the input geometry to the given product structure
.RE
.PP
\fB\-\-reactor\fR
.RS 4
experimental
.RE
.PP
\fB\-\-modef\fR \fIINT\fR
.RS 4
modefollowing algorithm\&.
\fIINT\fR
specifies the mode that should be used for the modefollowing\&.
.RE
.SS "GENERAL"
.PP
\fB\-I, \-\-input\fR \fIFILE\fR
.RS 4
use
\fIFILE\fR
as input source for
xcontrol(7)
instructions
.RE
.PP
\fB\-\-namespace\fR \fISTRING\fR
.RS 4
give this
xtb(1)
run a namespace\&. All files, even temporary ones, will be named according to
\fISTRING\fR
(might not work everywhere)\&.
.RE
.PP
\fB\-\-[no]copy\fR
.RS 4
copies the
xcontrol
file at startup (default = true)
.RE
.PP
\fB\-\-[no]restart\fR
.RS 4
restarts calculation from
xtbrestart
(default = true)
.RE
.PP
\fB\-P, \-\-parallel\fR \fIINT\fR
.RS 4
number of parallel processes
.RE
.PP
\fB\-\-define\fR
.RS 4
performs automatic check of input and terminate
.RE
.PP
\fB\-\-json\fR
.RS 4
write xtbout\&.json file
.RE
.PP
\fB\-\-citation\fR
.RS 4
print citation and terminate
.RE
.PP
\fB\-\-license\fR
.RS 4
print license and terminate
.RE
.PP
\fB\-v, \-\-verbose\fR
.RS 4
be more verbose (not supported in every unit)
.RE
.PP
\fB\-s, \-\-silent\fR
.RS 4
clutter the screen less (not supported in every unit)
.RE
.PP
\fB\-\-ceasefiles\fR
.RS 4
reduce the amount of output and files written
.RE
.PP
\fB\-\-strict\fR
.RS 4
turns all warnings into hard errors
.RE
.PP
\fB\-h, \-\-help\fR
.RS 4
show help page
.RE
.PP
\fB\-\-cut\fR
.RS 4
create inner region for
oniom
calculation without performing any calcultion
.RE
.SH "ENVIRONMENT VARIABLES"
.sp
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\&.
.sp
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\&.
.SH "LOCAL FILES"
.sp
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 \fB\-\-namespace\fR option\&.
.SS "INPUT"
.PP
\fB\&.CHRG\fR
.RS 4
molecular charge as
\fIint\fR
.RE
.PP
\fB\&.UHF\fR
.RS 4
Number of unpaired electrons as
\fIint\fR
.RE
.PP
\fBmdrestart\fR
.RS 4
contains restart information for MD,
\fB\-\-namespace\fR
compatible\&.
.RE
.PP
\fBpcharge\fR
.RS 4
point charge input, format is
\fIreal\fR
\fIreal\fR
\fIreal\fR
\fIreal\fR
[\fIint\fR]\&. 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\&.
.RE
.PP
\fBxcontrol\fR
.RS 4
default input file in
\fB\-\-copy\fR
mode, see
xcontrol(7)
for details, set by
\fB\-\-input\fR\&.
.RE
.PP
\fBxtbrestart\fR
.RS 4
contains restart information for SCC,
\fB\-\-namespace\fR
compatible\&.
.RE
.SS "OUTPUT"
.PP
\fBcharges\fR
.RS 4
contains Mulliken partial charges calculated in SCC
.RE
.PP
\fBwbo\fR
.RS 4
contains Wiberg bond order calculated in SCC,
\fB\-\-namespace\fR
compatible\&.
.RE
.PP
\fBenergy\fR
.RS 4
total energy in Turbomole format
.RE
.PP
\fBgradient\fR
.RS 4
geometry, energy and gradient in Turbomole format
.RE
.PP
\fBhessian\fR
.RS 4
contains the (not mass weighted) cartesian Hessian,
\fB\-\-namespace\fR
compatible\&.
.RE
.PP
\fBxtbopt\&.xyz\fR, \fBxtbopt\&.coord\fR
.RS 4
optimized geometry in the same format as the input geometry\&.
.RE
.PP
\fBxtbhess\&.coord\fR
.RS 4
distorted geometry if imaginary frequency was found
.RE
.PP
\fBxtbopt\&.log\fR
.RS 4
contains all structures obtained in the geometry optimization with the respective energy in the comment line in a XMOL formatted trajectory
.RE
.PP
\fBxtbsiman\&.log\fR,\fBxtb\&.trj\&.\fR\fB\fIint\fR\fR
.RS 4
trajectories from MD
.RE
.PP
\fBscoord\&.\fR\fB\fIint\fR\fR
.RS 4
coordinate dump of MD
.RE
.PP
\fBfod\&.cub\fR
.RS 4
FOD on a cube\-type grid
.RE
.PP
\fBspindensity\&.cub\fR
.RS 4
spindensity on a cube\-type grid
.RE
.PP
\fBdensity\&.cub\fR
.RS 4
density on a cube\-type grid
.RE
.PP
\fBmolden\&.input\fR
.RS 4
MOs and occupation for visualisation and sTDA\-xTB calculations
.RE
.PP
\fBpcgrad\fR
.RS 4
gradient of the point charges
.RE
.PP
\fBxtb_esp\&.cosmo\fR
.RS 4
ESP fake cosmo output
.RE
.PP
\fBxtb_esp_profile\&.dat\fR
.RS 4
ESP histogramm data
.RE
.PP
\fBvibspectrum\fR
.RS 4
Turbomole style vibrational spectrum data group
.RE
.PP
\fBg98\&.out\fR, \fBg98l\&.out\fR, \fBg98_canmode\&.out\fR, \fBg98_locmode\&.out\fR
.RS 4
g98 fake output with normal or local modes
.RE
.PP
\fB\&.tmpxtbmodef\fR
.RS 4
input for mode following
.RE
.PP
\fBcoordprot\&.0\fR
.RS 4
protonated species
.RE
.PP
\fBxtblmoinfo\fR
.RS 4
centers of the localized molecular orbitals
.RE
.PP
\fBlmocent\&.coord\fR
.RS 4
centers of the localized molecular orbitals
.RE
.PP
\fBtmpxx\fR
.RS 4
number of recommended modes for mode following
.RE
.PP
\fBxtb_normalmodes\fR, \fBxtb_localmodes\fR
.RS 4
binary dump for mode following
.RE
.SS "TOUCH"
.PP
\fBxtbmdok\fR
.RS 4
generated by successful MD
.RE
.PP
\fB\&.xtbok\fR
.RS 4
generated after each successful
xtb(1)
run
.RE
.PP
\fB\&.sccnotconverged\fR
.RS 4
generated after failed SCC with printlevel=2
.RE
.SH "WARNINGS"
.sp
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 \fB\-\-define\fR flag\&. Please, study this warnings carefully!
.sp
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\&.
.sp
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:
.PP
\fBANCopt failed to converge the optimization\fR
.RS 4
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\&.
.RE
.PP
\fBHessian on incompletely optimized geometry!\fR
.RS 4
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\&.
.RE
.SH "EXIT STATUS"
.PP
\fB0\fR
.RS 4
normal termination of
xtb(1)
.RE
.PP
\fB128\fR
.RS 4
Failure (termination via error stop generates 128 as return value)
.RE
.SH "BUGS"
.sp
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
.SH "RESOURCES"
.sp
Main web site: http://grimme\&.uni\-bonn\&.de/software/xtb
.SH "COPYING"
.sp
Copyright \(co 2017\-2023 Stefan Grimme
.sp
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\&.
.sp
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\&.
.sp
You should have received a copy of the GNU Lesser General Public License along with xtb\&. If not, see https://www\&.gnu\&.org/licenses/\&.