1) About GAMESS: GAMESS is a program for ab initio molecular quantum chemistry. Acronym GAMESS stands for General Atomic and Molecular Electronic Structure System. There are two main versions of GAMESS: GAMESS(US) and GAMESS (UK). We will talk here about former. It was written and supported mostly by Mark Gordon's Quantum Theory Group from Iowa State University. 2) How to obtain GAMESS: GAMESS is available at no cost to both academic and industrial users. You can download its source code and documentation from web-site: http://www.msg.chem.iastate.edu/gamess. Authors claim that "GAMESS runs on nearly all computer systems, from large parallel systems to workstations to desktops to laptops, in scalar or parallel fashion". "GAMESS' source can be compiled for Apple systems running OS X, or for PC systems running Linux or Windows". 3) Summary of main GAMESS' Capabilities (see for details file intro.pdf in GAMESS' documentation) : 1. Methods: a) Calculates SCF (Self-Consistent Field) molecular wavefunctions using Hartree-Fock methods (Restricted RHF, Unrestricted UHF, Restricted Open-shell ROHF) b) Calculates the electron correlation energy correction for these SCF wavefunctions using Density Functional Theory (DFT), Configuration Interaction (CI), Many Body Perturbation Theory (MP2), Coupled-Cluster (CC) c) Calculates semi-empirical Modified Neglect of Diatomic Overlap (MNDO), Austin Model 1 (AM1), and parametric method 3 (PM3) models 2. Results: a) energy (default) b) charge distribution and polarizabilities (both the static and frequency dependent) c) potential energy surface (in particular, it calculates energy gradients, optimizes molecular geometries, searches for saddle points (transition states), traces the intrinsic reaction path from the saddle point towards products, or back to reactants) d) normal modes, vibrational frequencies, and IR intensities. Raman intensities are optional e) excited state energies, wavefunctions, and transition dipole moments Many of those calculations can be done in parallel! 3. Limitations: GAMESS is limited to a total of 2,000 atoms. The total number of symmetry unique basis set shells cannot exceed 5,000, containing no more than 20,000 Gaussians. In practice, you will probably run out of CPU time or disk storage before you encounter any of these limitations. 4) Using GAMESS: 1. Before running GAMESS one needs: a) create working directory (for example, ~$USER/gamess) and two subdirectories scr and mcpdata there b) copy C-shell script rungms from GAMESS directory into your work directory and modify following lines in it: set GMSPATH=/usr/local/gamess_2006/gamess set SCR=~$USER/gamess/scr setenv MCPPATH ~$USER/gamess/mcpdata set TARGET=sockets where '/usr/local/gamess_2006/gamess' is the directory where GAMESS is installed c) if you want to run parallel calculations you need to specify number nodes, processors and the node list in rungms as followings: if ($NCPUS > 1) then set NNODES=4 set NCPUS=8 set HOSTLIST=(master2:cpus=2 node5:cpus=2 node6:cpus=2 node7:cpus=2) endif 2. Running GAMESS We run GAMESS with the script rungms by typing ./rungms JOB VERNO NCPUS >& JOB.log & where JOB is the name of the 'JOB.inp' file to be executed, VERNO is the number of the executable you chose at 'lked' time, NCPUS is the number of processors to be used. Note the paramaters VERNO and NCPUS can be omitted. In that case GAMESS uses their default values VERNO=00 and NCPUS=1. 5) Input file format (files intro.pdf and input.pdf): Input to GAMESS may be in upper or lower case. All input groups begin with a $ sign in column 2, followed by a name identifying that group, and end with keyword $END appearing anywhere. There are three types of input in GAMESS 1. The most of groups are namelist-like with keywords in form "name"="value" given in arbitrary order. Example. Chemical control data group ($CONTRL): $CONTRL SCFTYP=RHF RUNTYP=OPTIMIZE $END The first keyword (SCFTYP) specifies the type of wavefunctions (RHF) and the second one (RUNTYP) specifies the type of computation (OPTIMIZE optimizes the molecular geometry) 2. Few groups are free format groups without keywords. The first line of these will contain only the group name, followed by several lines of positional data usually with no keywords, and a last line containing " $END" only. The most important example of this type is $DATA which gives molecule geometry and basis set. This group is the only one which is always required. The rest of the groups can be omitted if the program defaults are adequate. Example of $DATA group: $DATA STO-3G test case for water CNV 2 OXYGEN 8.0 STO 3 HYDROGEN 1.0 -0.758 0.0 0.545 STO 3 $END The second line is the title. The next one is the Schoenflies symbol of the symmetry group and the order of the highest rotation axis. The line after that specifies atom name, nuclear charge and coordinates. The missing values will be read as zero, so that the oxygen is placed at the origin. The next line specifies basis set and the number of Gaussians if a Pople basis set is used. You can omit this line if the basis set is given in $BASIS group. Note there is only one HYDROGEN atom given in the $DATA group. The second HYDROGEN atom is generated automatically according to the symmetry of the molecule (C2V). 3. Formatted data. This data is NEVER typed by the user, but rather is generated in the correct format by some earlier GAMESS run. This can be, for instance, the molecular orbitals. 6) Examples 1. Geometry optimization (CH2, exam01.inp) $CONTRL SCFTYP=UHF RUNTYP=OPTIMIZE MULT=3 COORD=ZMT NZVAR=0 $END $SYSTEM TIMLIM=10 MEMORY=100000 $END $STATPT OPTTOL=1.0E-5 $END $BASIS GBASIS=STO NGAUSS=3 $END $GUESS GUESS=HUCKEL $END $DATA Methylene...1-A-1 state...RHF/STO-3G Cnv 2 C H 1 rCH H 1 rCH 2 aHCH rCH=1.29 aHCH=160.0 $END The coordinates in the $DATA group are given Z-Matrix form which is indicated by COORD=ZMT in the $CONTROL group. The group $GUESS controls the selection of initial molecular orbitals. With GUESS=HUCKEL it uses an extended Huckel calculation. The equilibrium geometry has been found after 5 iterations and it is given by rCH=1.0820447 aHCH=125.5211256 TOTAL ENERGY (before) = -38.3620796981 TOTAL ENERGY (after) = -38.4362343271 2. Charges calculation (H2O, water.inp) $CONTRL SCFTYP=RHF COORD=ZMT ICHARG=0 EXETYP=RUN DFTTYP=B3LYP $END $BASIS GBASIS=N31 NGAUSS=6 NDFUNC=3 $END $system timlim=1 mwords=12 $end $SCF DIRSCF=.TRUE. $END $guess guess=huckel $end $ELPOT IEPOT=1 WHERE=PDC $END $PDC PTSEL=CHELPG CONSTR=CHARGE $END $data calculation atomic charges for water molecule Cnv 2 O H 1 rOH H 1 rOH 2 aHOH rOH=0.9578 aHOH=104.48 $end To calculate the charges distribution we fit atomic charges to reproduce the electrostatic potential. One needs to set keywords IEPOT=1 and WHERE=PDC in the group $ELPOT. The group $PDC determines the points at which to compute the electrostatic potential. PTSEL=CHELPG to use a modified version of the CHELPG algorithm, which produces a symmetric grid of points for a symmetric molecule CONSTR=CHARGE means that the sum of fitted atomic charges is constrained to reproduce the total molecular charge. ----------------------- ELECTROSTATIC POTENTIAL ----------------------- BRENEMAN (CHELPG) RADII USED FOR CHARGE FITTING NUMBER OF POINTS SELECTED FOR FITTING = 256 NET CHARGES: ------------------------------------- ATOM CHARGE E.S.D. ------------------------------------- O -0.6574 0.0068 H 0.3287 0.0044 H 0.3287 0.0044 ------------------------------------- RMS DEVIATION IS 1.759 KCAL/MOLE RELATIVE RMS DEVIATION IS 16.107 % MULTIPOLE MOMENTS: --------------------------------------------------------- STATUS ACTUAL VALUE QUANTITY FITTED VALUE --------------------------------------------------------- FIXED 0.0000 TOTAL CHARGE 0.0000 1.8042 D DIPOLE MOMENT 1.8519 D The experimantal value for the dipole moment is 1.847 D.