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            If you have problems during the execution of MRCC, please attach the output with an adequate description of your case as well as the followings:
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Switching to another root during CCSD calculation of N2 triplet
- Jos Suijker
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                4 years 1 month ago                #1163
        by Jos Suijker
    
    
 	
					
                                	
			
				    
            
            
            
            
            
                                
    
                                                
    
        Switching to another root during CCSD calculation of N2 triplet was created by Jos Suijker            
    
        Dear Forum,
We calculate the energy of the lowest triplet of N2 by MCSCF followed by the CCSD calculation. Using the patches posted on the MRCC website convergence of my calculations require much less iterations then in the un-patched version and we get convergence also at longer bondlength's. In the un-patched version the calculation does not converge at longer N-N bond length's.
It seems however that the calculation switches to another root during its iterations. for example at bond length R1=1.7775 The calculation is almost converged in iteration 23 to an energy that seems right to me (comparing with the energy found at a little smaller bond length) at iteration 24 however the solution makes a jump and converges to this root. (output is attached). The same effect is also visible in the un-patched version although there is no convergence in that case
Is there a setting that might prevent this jump?
Thanks in advance for any help.
Jos Suijker
Technical University of Eindhoven
The Netherlands
    We calculate the energy of the lowest triplet of N2 by MCSCF followed by the CCSD calculation. Using the patches posted on the MRCC website convergence of my calculations require much less iterations then in the un-patched version and we get convergence also at longer bondlength's. In the un-patched version the calculation does not converge at longer N-N bond length's.
It seems however that the calculation switches to another root during its iterations. for example at bond length R1=1.7775 The calculation is almost converged in iteration 23 to an energy that seems right to me (comparing with the energy found at a little smaller bond length) at iteration 24 however the solution makes a jump and converges to this root. (output is attached). The same effect is also visible in the un-patched version although there is no convergence in that case
Is there a setting that might prevent this jump?
Thanks in advance for any help.
Jos Suijker
Technical University of Eindhoven
The Netherlands
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- kallay
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         - Mihaly Kallay
 
            
        
                4 years 1 month ago                #1164
        by kallay
    
    
            
Best regards,
Mihaly Kallay
    
    
            
            
            
            
                                
    
                                                
    
        Replied by kallay on topic Switching to another root during CCSD calculation of N2 triplet            
    
        Dear Jos,
You should try root following, that is, set diag=follow in the input.
            You should try root following, that is, set diag=follow in the input.
Best regards,
Mihaly Kallay
        The following user(s) said Thank You: Jos Suijker     
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                4 years 1 month ago                #1165
        by Jos Suijker
    
    
            
            
            
            
            
                                
    
                                                
    
        Replied by Jos Suijker on topic Switching to another root during CCSD calculation of N2 triplet            
    
        Dear Prof. Kallay
Thank you very much, this solution worked perfect. The calculation converged easily last night. We should have found this keyword ourselves in the manual it is there.
Regards,
Jos Suijker
    Thank you very much, this solution worked perfect. The calculation converged easily last night. We should have found this keyword ourselves in the manual it is there.
Regards,
Jos Suijker
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